Energy conversion apparatus

ABSTRACT

An engine body may include a piston body comprising a piston chamber and a regenerator body comprising a regenerator conduit. An engine body may include a working-fluid heat exchanger body comprising a plurality of working-fluid pathways fluidly communicating between the piston chamber and the regenerator conduit. Additionally, or alternatively, an engine body may include a heater body comprising a plurality of heating fluid pathways and the plurality of working-fluid pathways. The heating fluid pathways may have a heat transfer relationship with the working fluid pathways. The working-fluid pathways may fluidly communicate between the piston chamber and the regenerator conduit. The engine body may include a monolithic body defined at least in part by the piston body, the regenerator body, and the working-fluid heat exchanger body, and/or defined at least in part by the piston body, the regenerator body, and the heater body.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/878,858, filed on May 20, 2020, which claims priority to each of thefollowing U.S. Provisional applications, the contents of which areincorporated herein by reference in their entirety for all purposes asif set forth verbatim: App. No. 62/850,599, filed May 21, 2019; App. No.62/850,623, filed May 21, 2019; App. No. 62/850,678, filed May 21, 2019;App. No. 62/850,692, filed May 21, 2019; and App. No. 62/850,701, filedMay 21, 2019. The present application also incorporates by referenceInternational Patent Application Number 503221-US-2/GE3D-334-1 filed onMay 20, 2020 in its entirety for all purposes.

FIELD

The present subject matter relates generally to energy conversionsystems, power generation systems, and energy distribution systems. Thepresent subject matter additionally relates to heat exchangers and heatexchanger systems. The present subject matter further relates to pistonengine assemblies, such as closed-cycle engine systems. The presentsubject matter still further relates to systems and methods for controlor operation of one or more systems of the present subject matterherein.

BACKGROUND

Power generation and distribution systems are challenged to provideimproved power generation efficiency and/or lowered emissions.Furthermore, power generation and distribution systems are challenged toprovide improved power output with lower transmission losses. Certainpower generation and distribution systems are further challenged toimprove sizing, portability, or power density generally while improvingpower generation efficiency, power output, and emissions.

Certain engine system arrangements, such as closed cycle engines, mayoffer some improved efficiency over other engine system arrangements.However, closed cycle engine arrangements, such as Stirling engines, arechallenged to provide relatively larger power output or power density,or improved efficiency, relative to other engine arrangements. Closedcycle engines may suffer due to inefficient combustion, inefficient heatexchangers, inefficient mass transfer, heat losses to the environment,non-ideal behavior of the working fluid(s), imperfect seals, friction,pumping losses, and/or other inefficiencies and imperfections. As such,there is a need for improved closed cycle engines and systemarrangements that may provide improved power output, improved powerdensity, or further improved efficiency. Additionally, there is a needfor an improved closed cycle engine that may be provided to improvepower generation and power distribution systems.

Additionally, or alternatively, there is a general need for improvedheat transfer devices, such as for heat engines, or as may be applied topower generation systems, distribution systems, propulsion systems,vehicle systems, or industrial or residential facilities.

Furthermore, there is a need for improved control system and methods foroperating power generation systems as may include subsystems thatcollectively may provide improved power generation efficiency or reducedemissions.

BRIEF DESCRIPTION

Aspects and advantages will be set forth in part in the followingdescription, or may be apparent from the description, or may be learnedthrough practicing the presently disclosed subject matter.

In one aspect, the present disclosure embraces monolithic engineassemblies. An exemplary monolithic engine assembly may include anengine body that includes a regenerator body. The engine body and theregenerator body may respectively define at least a portion of amonolithic body, or the engine body may define at least a portion of afirst monolithic body-segment and the regenerator body may define atleast a portion of a second monolithic body-segment operably coupled oroperably couplable to the first monolithic body-segment.

In another aspect, the present disclosure embraces regenerator bodies,such as monolithic regenerator bodies. An exemplary regenerator body mayinclude a regenerator conduit, and a plurality of fin arrays adjacentlydisposed within the regenerator conduit and respectively supported bythe regenerator conduit in spaced relation to one another. The spacedrelation of the plurality of fin arrays may define a gap longitudinallyseparating adjacent ones of the plurality of fin arrays.

These and other features, aspects and advantages will become betterunderstood with reference to the following description and appendedclaims. The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate exemplaryembodiments and, together with the description, serve to explain certainprinciples of the presently disclosed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure including the best mode, directed to oneof ordinary skill in the art, is set forth in the specification, whichmakes reference to the appended figures, in which:

FIG. 1 is a schematic block diagram depicting a system for energyconversion according to an aspect of the present disclosure;

FIG. 2 is a cross sectional view of an exemplary embodiment of a closedcycle engine and load device according to an aspect of the presentdisclosure;

FIG. 3A schematically depicts an exemplary regenerator system of anengine according to an aspect of the present disclosure;

FIG. 3B schematically depicts a cross-sectional view of an exemplaryregenerator body in relation to a portion of an engine according to anaspect of the present disclosure;

FIG. 3C schematically depicts a top cross-sectional view of theexemplary regenerator body of FIG. 3B;

FIG. 3D schematically depicts an enlarged perspective cross-sectionalview of the exemplary regenerator body of FIG. 3B;

FIG. 4A schematically depicts a cross-sectional view of anotherexemplary regenerator body;

FIG. 4B schematically depicts a cross-sectional view of yet anotherexemplary regenerator body;

FIG. 5 schematically depicts a perspective view of a plurality of finarrays that may be included in a regenerator body, such as theregenerator body shown in FIG. 3A or 3B;

FIG. 6A schematically depicts a perspective cross-sectional view ofanother exemplary plurality of fin arrays that may be included in aregenerator body, such as the regenerator body shown in FIG. 4B;

FIG. 6B schematically depicts an exemplary fin array from the exemplaryplurality of fin arrays shown in FIG. 6A;

FIG. 7 schematically depicts a side view of the plurality of fin arraysshown in FIGS. 5 and/or 6A;

FIG. 8A schematically depicts a perspective view of a fin array from theplurality of fin arrays shown in FIG. 5;

FIG. 8B schematically depicts a right-side view of the fin array shownin FIG. 8A;

FIG. 8C schematically depicts a side view of the fin array viewing thefin array perpendicular to the perspective shown in FIG. 8A;

FIG. 8D schematically depicts a plurality of fins from the fin arrayshown in FIG. 8A viewed from the perspective shown in FIG. 8C;

FIGS. 9A-9F schematically depict exemplary regenerator bodyconfigurations; and

FIG. 10 shows a flowchart depicting an exemplary method of regeneratingheat in an engine-working fluid;

FIGS. 11A and 11B schematically depict exploded views of exemplaryengine assemblies according to aspects of the present disclosure;

FIG. 12 schematically depicts an enlarged partial exploded view ofanother exemplary engine assembly according to aspects of the presentdisclosure; and

FIG. 13 shows a flowchart depicting an exemplary method of building anengine assembly.

FIG. 14 schematically depicts a cross-sectional view of an exemplaryclosed-cycle engine, which may be a regenerative heat engine and/or aStirling engine;

FIG. 15 schematically depicts an exemplary heater bodies, which, forexample, may be included in the closed-cycle engine shown in FIG. 14;

FIG. 16 schematically depicts a cross-sectional perspective view of anexemplary heater body, which, for example, may be included in theclosed-cycle engine shown in FIG. 14;

FIG. 17 schematically depicts exemplary monolithic bodies, which mayinclude monolithic body portions and/or monolithic body-segments.

FIG. 18 shows a top cross-sectional view of the exemplary heat exchangerbody, with a plurality of heat transfer regions indicated; and

FIG. 19 schematically depicts a bottom cross-sectional view of anexemplary working-fluid body;

FIG. 20 schematically depicts a bottom perspective view of an exemplaryworking-fluid body; and

FIG. 21 provides an example computing system in accordance with anexample embodiment of the present disclosure.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the disclosure,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the disclosure and notlimitation. In fact, it will be apparent to those skilled in the artthat various modifications and variations can be made in the presentdisclosure without departing from the scope of the disclosure. Forinstance, features illustrated or described as part of one embodimentcan be used with another embodiment to yield a still further embodiment.In another instance, ranges, ratios, or limits associated herein may bealtered to provide further embodiments, and all such embodiments arewithin the scope of the present disclosure. Unless otherwise specified,in various embodiments in which a unit is provided relative to a ratio,range, or limit, units may be altered, and/or subsequently, ranges,ratios, or limits associated thereto are within the scope of the presentdisclosure. Thus, it is intended that the present disclosure covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

It is understood that terms “upstream” and “downstream” refer to therelative direction with respect to fluid flow in a fluid pathway. Forexample, “upstream” refers to the direction from which the fluid flows,and “downstream” refers to the direction to which the fluid flows. It isalso understood that terms such as “top”, “bottom”, “outward”, “inward”,and the like are words of convenience and are not to be construed aslimiting terms. As used herein, the terms “first”, “second”, and “third”may be used interchangeably to distinguish one component from anotherand are not intended to signify location or importance of the individualcomponents. The terms “a” and “an” do not denote a limitation ofquantity, but rather denote the presence of at least one of thereferenced item.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” “substantially,” and “approximately,” are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value, or the precision of the methodsor machines for constructing or manufacturing the components and/orsystems. For example, the approximating language may refer to beingwithin a 10 percent margin.

Here and throughout the specification and claims, range limitations arecombined and interchanged, such ranges are identified and include allthe sub-ranges contained therein unless context or language indicatesotherwise. For example, all ranges disclosed herein are inclusive of theendpoints, and the endpoints are independently combinable with eachother.

The heat transfer relationships described herein may include thermalcommunication by conduction and/or convection. A heat transferrelationship may include a thermally conductive relationship thatprovides heat transfer through conduction (e.g., heat diffusion) betweensolid bodies and/or between a solid body and a fluid. Additionally, orin the alternative, a heat transfer relationship may include a thermallyconvective relationship that provides heat transfer through convection(e.g., heat transfer by bulk fluid flow) between a fluid and a solidbody. It will be appreciated that convection generally includes acombination of a conduction (e.g., heat diffusion) and advection (e.g.,heat transfer by bulk fluid flow). As used herein, reference to athermally conductive relationship may include conduction and/orconvection; whereas reference to a thermally convective relationshipincludes at least some convection.

A thermally conductive relationship may include thermal communication byconduction between a first solid body and a second solid body, between afirst fluid and a first solid body, between the first solid body and asecond fluid, and/or between the second solid body and a second fluid.For example, such conduction may provide heat transfer from a firstfluid to a first solid body and/or from the first solid body to a secondfluid. Additionally, or in the alternative, such conduction may provideheat transfer from a first fluid to a first solid body and/or through afirst solid body (e.g., from one surface to another) and/or from thefirst solid body to a second solid body and/or through a second solidbody (e.g., from one surface to another) and/or from the second solidbody to a second fluid.

A thermally convective relationship may include thermal communication byconvection (e.g., heat transfer by bulk fluid flow) between a firstfluid and a first solid body, between the first solid body and a secondfluid, and/or between a second solid body and a second fluid. Forexample, such convection may provide heat transfer from a first fluid toa first solid body and/or from the first solid body to a second fluid.Additionally, or in the alternative, such convection may provide heattransfer from a second solid body to a second fluid.

It will be appreciated that the terms “clockwise” and“counter-clockwise” are terms of convenience and are not to be limiting.Generally, the terms “clock-wise” and “counter-clockwise” have theirordinary meaning, and unless otherwise indicated refer to a directionwith reference to a top-down or upright view. Clockwise andcounter-clockwise elements may be interchanged without departing fromthe scope of the present disclosure.

Where temperatures, pressures, loads, phases, etc. are said to besubstantially similar or uniform, it should be appreciated that it isunderstood that variations, leakages, or other minor differences ininputs or outputs may exist such that the differences may be considerednegligible by one skilled in the art. Additionally, or alternatively,where temperatures or pressures are said to be uniform, i.e., asubstantially uniform unit (e.g., a substantially uniform temperature atthe plurality of chambers A221), it should be appreciated that in oneembodiment, the substantially uniform unit is relative to an averageoperating condition, such as a phase of operation of the engine, orthermal energy flow from one fluid to another fluid, or from one surfaceto a fluid, or from one surface to another surface, or from one fluid toanother surface, etc. For example, where a substantially uniformtemperature is provided or removed to/from the plurality of chambersA221, A222, the temperature is relative to an average temperature over aphase of operation of the engine. As another example, where asubstantially uniform thermal energy unit is provided or removed to/fromthe plurality of chambers A221, A222, the uniform thermal energy unit isrelative to an average thermal energy supply from one fluid to anotherfluid relative to the structure, or plurality of structures, throughwhich thermal energy transferred.

Various interfaces, such as mating surfaces, interfaces, points,flanges, etc. at which one or more monolithic bodies, or portionsthereof, attach, couple, connect, or otherwise mate, may define orinclude seal interfaces, such as, but not limited to, labyrinth seals,grooves into which a seal is placed, crush seals, gaskets, vulcanizingsilicone, etc., or other appropriate seal or sealing substance.Additionally, or alternatively, one or more of such interfaces may becoupled together via mechanical fasteners, such as, but not limited to,nuts, bolts, screws, tie rods, clamps, etc. In still additional oralternative embodiments, one or more of such interfaces may be coupledtogether via a joining or bonding processes, such as, but not limitedto, welding, soldering, brazing, etc., or other appropriate joiningprocess. It should be appreciated that ratios, ranges, minimums,maximums, or limits generally, or combinations thereof, may providestructure with benefits not previously known in the art. As such, valuesbelow certain minimums described herein, or values above certainmaximums described herein, may alter the function and/or structure ofone or more components, features, or elements described herein. Forexample, ratios of volumes, surface area to volume, power output tovolume, etc. below the ranges described herein may be insufficient fordesired thermal energy transfer, such as to undesirably limit poweroutput, efficiency, or Beale number. As another example, limits greaterthan those described herein may undesirably increase the size,dimensions, weight, or overall packaging of the system or engine, suchas to undesirably limit the applications, apparatuses, vehicles,usability, utility, etc. in which the system or engine may be applied oroperated. Still further, or alternatively, undesired increases inoverall packaging may undesirably decrease efficiency of an overallsystem, application, apparatus, vehicle, etc. into which the engine maybe installed, utilized, or otherwise operated. For example, although anengine may be constructed defining a similar or greater efficiency asdescribed herein, such an engine may be of undesirable size, dimension,weight, or overall packaging such as to reduce an efficiency of thesystem into which the engine is installed. As such, obviation ortransgression of one or more limits described herein, such as one orlimits relative to features such as, but not limited to, heaterconduits, chiller conduits A54, chamber volumes, walled conduit volumes,or operational temperatures, or combinations thereof, may undesirablyalter such structures such as to change the function of the system orengine.

Referring now to FIG. 1, an exemplary schematic block diagram depictinga system for energy conversion (hereinafter, “system A10”) is provided.Various embodiments of the system A10 provided herein include systemsfor power generation, a heat recovery system, a heat pump or cryogeniccooler, a system including and/or acting as a bottoming cycle and/or atopping cycle, or other system for producing useful work or energy, orcombinations thereof. Referring additionally for FIG. 2, variousembodiments of the system A10 include a closed cycle engine apparatus(hereinafter, “engine A100”, apparatus “A100”, or “engine assemblyC900”, or otherwise denoted herein) operably coupled to a load devicec092. The engine A100 contains a substantially fixed mass of an engineworking fluid to which and from which thermal energy is exchanged at arespective cold side heat exchanger A42 and a hot side heat exchangerC108. In one embodiment, the engine working fluid is helium. In otherembodiments, the engine working fluid may include air, nitrogen,hydrogen, helium, or any appropriate compressible fluid, or combinationsthereof. In still various embodiments, any suitable engine working fluidmay be utilized in accordance with the present disclosure. In exemplaryembodiments, the engine working fluid may include a gas, such as aninert gas. For example, a noble gas, such as helium may be utilized asthe engine working fluid. Exemplary working fluids preferably are inert,such that they generally do not participate in chemical reactions suchas oxidation within the environment of the engine. Exemplary noblegasses include monoatomic gases such as helium, neon, argon, krypton, orxenon, as well as combinations of these. In some embodiments, the engineworking fluid may include air, oxygen, nitrogen, or carbon dioxide, aswell as combinations of these. In still various embodiments, the engineworking fluid may be liquid fluids of one or more elements describedherein, or combinations thereof. It should further be appreciated thatvarious embodiments of the engine working fluid may include particles orother substances as appropriate for the engine working fluid.

In various embodiments, the load device C092 is a mechanical work deviceor an electric machine. In one embodiment, the load device C092 is apump, compressor, or other work device. In another embodiment, the loaddevice C092 as an electric machine is configured as a generatorproducing electric energy from movement of a piston assembly A1010 atthe engine. In still another embodiment, the electric machine isconfigured as a motor providing motive force to move or actuate thepiston assembly A1010, such as to provide initial movement (e.g., astarter motor). In still various embodiments, the electric machinedefines a motor and generator or other electric machine apparatus suchas described further herein.

A heater body C100 is thermally coupled to the engine A100. The heaterbody C100 may generally define any apparatus for producing or otherwiseproviding a heating working fluid such as to provide thermal energy tothe engine working fluid. Various embodiments of the heater body C100are further provided herein. Exemplary heater bodies C100 may include,but are not limited to, a combustion or detonation assembly, an electricheater, a nuclear energy source, a renewable energy source such as solarpower, a fuel cell, a heat recovery system, or as a bottoming cycle toanother system. Exemplary heater bodies C100 at which a heat recoverysystem may be defined include, but are not limited to, industrial wasteheat generally, gas or steam turbine waste heat, nuclear waste heat,geothermal energy, decomposition of agricultural or animal waste, moltenearth or metal or steel mill gases, industrial drying systems generallyor kilns, or fuel cells. The exemplary heater body C100 providingthermal energy to the engine working fluid may include all or part of acombined heat and power cycle, or cogeneration system, or powergeneration system generally.

In still various embodiments, the heater body C100 is configured toprovide thermal energy to the engine working fluid via a heating workingfluid. The heating working fluid may be based, at least in part, on heatand liquid, gaseous, or other fluid provided by one or more fuel sourcesand oxidizer sources providing a fuel and oxidizer. In variousembodiments, the fuel includes, but is not limited to, hydrocarbons andhydrocarbon mixtures generally, “wet” gases including a portion ofliquid (e.g., humid gas saturated with liquid vapor, multiphase flowwith approximately 10% liquid and approximately 90% gas, natural gasmixed with oil, or other liquid and gas combinations, etc.), petroleumor oil (e.g., Arabian Extra Light Crude Oil, Arabian Super Light, LightCrude Oil, Medium Crude Oil, Heavy Crude Oil, Heavy Fuel Oil, etc.),natural gas (e.g., including sour gas), biodiesel condensate or naturalgas liquids (e.g., including liquid natural gas (LNG)), dimethyl ether(DME), distillate oil #2 (DO2), ethane (C2), methane, high H2 fuels,fuels including hydrogen blends (e.g., propane, butane, liquefiedpetroleum gas, naphtha, etc.), diesel, kerosene (e.g., jet fuel, suchas, but not limited to, Jet A, Jet A-1, JP1, etc.), alcohols (e.g.,methanol, ethanol, etc.), synthesis gas, coke over gas, landfill gases,etc., or combinations thereof.

In various embodiments, the system A10 includes a working fluid bodyC108, such as further described herein. In one embodiment, the workingfluid body C108 defines a hot side heat exchanger A160, such as furtherdescribed herein, from which thermal energy is output to the engineworking fluid at an expansion chamber A221 of the engine. The workingfluid body C108 is positioned at the expansion chamber A221 of theengine in thermal communication with the heater body C100. In otherembodiments, the working fluid body C108 may be separate from the heaterbody C100, such that the heating working fluid is provided in thermalcommunication, or additionally, in fluid communication with the workingfluid body C108. In particular embodiments, the working fluid body C108is positioned in direct thermal communication with the heater body C100and the expansion chamber A221 of the engine A100 such as to receivethermal energy from the heater body C100 and provide thermal energy tothe engine working fluid within the engine.

In still various embodiments, the heater body C100 may include a singlethermal energy output source to a single expansion chamber A221 of theengine. As such, the system A10 may include a plurality of heaterassemblies each providing thermal energy to the engine working fluid ateach expansion chamber A221. In other embodiments, such as depicted inregard to FIG. 2, the heater body C100 may provide thermal energy to aplurality of expansion chambers A221 of the engine. In still otherembodiments, the heater body includes a single thermal energy outputsource to all expansion chambers A221 of the engine.

The system A10 further includes a chiller assembly, such as chillerassembly A40 further described herein. The chiller assembly A40 isconfigured to receive and displace thermal energy from a compressionchamber A222 of the engine. The system A10 includes a cold side heatexchanger A42 thermally coupled to the compression chamber A222 of theclosed cycle engine and the chiller assembly. In one embodiment, thecold side heat exchanger A42 and the piston body C700 defining thecompression chamber A222 of the engine are together defined as anintegral, unitary structure. In still various embodiments, the cold sideheat exchanger A42, at least a portion of the piston body C700 definingthe compression chamber A222, and at least a portion of the chillerassembly together define an integral, unitary structure.

In various embodiments, the chiller assembly A40 is a bottoming cycle tothe engine A100. As such, the chiller assembly A40 is configured toreceive thermal energy from the engine A100. The thermal energy receivedat the chiller assembly A40, such as through a cold side heat exchangerA42, or cold side heat exchanger A170 further herein, from the engineA100 is added to a chiller working fluid at the chiller assembly A40. Invarious embodiments, the chiller assembly A40 defines a Rankine cyclesystem through which the chiller working fluid flows in closed looparrangement with a compressor. In some embodiments, the chiller workingfluid is further in closed loop arrangement with an expander. In variousembodiments, the heat exchanger A188 may include a condenser orradiator. The cold side heat exchanger A40 is positioned downstream ofthe compressor and upstream of the expander and in thermal communicationwith a compression chamber A222 of the closed cycle engine, such asfurther depicted and described in regard to FIG. 2. In variousembodiments, the cold side heat exchanger A42 may generally define anevaporator receiving thermal energy from the engine A40.

Referring still to FIG. 1, in some embodiments, the heat exchanger A188is positioned downstream of the expander and upstream of the compressorand in thermal communication with a cooling working fluid. In theschematic block diagram provided in FIG. 1, the cooling working fluid isan air source. However, in various embodiments, the cooling fluid maydefine any suitable fluid in thermal communication with the heatexchanger. The heat exchanger may further define a radiator configuredto emit or dispense thermal energy from the chiller assembly A40. A flowof cooling working fluid from a cooling fluid source is provided inthermal communication with the heat exchanger to further aid heattransfer from the chiller working fluid within the chiller assembly A40to the cooling working fluid.

As further described herein, in various embodiments the chiller assemblyA40 may include a substantially constant density heat exchanger. Theconstant density heat exchanger generally includes a chamber includingan inlet and an outlet each configured to contain or trap a portion ofthe chiller working fluid for a period of time as heat from the closedcycle engine is transferred to the cold side heat exchanger A42. Invarious embodiments, the chamber may define a linear or rotary chamberat which the inlet and the outlet are periodically opened and closed viavalves or ports such as to trap the chiller working fluid within thechamber for the desired amount of time. In still various embodiments,the rate at which the inlet and the outlet of the chamber defining theconstant density heat exchanger is a function at least of velocity of aparticle of fluid trapped within the chamber between the inlet and theoutlet. The chiller assembly A40 including the constant density heatexchanger may provide efficiencies, or efficiency increases,performances, power densities, etc. at the system A10 such as furtherdescribed herein.

It should be appreciated that in other embodiments, the chiller assemblyA40 of the system A10 may include a thermal energy sink generally. Forexample, the chiller assembly A40 may include a body of water, thevacuum of space, ambient air, liquid metal, inert gas, etc. In stillvarious embodiments, the chiller working fluid at the chiller assemblyA40 may include, but is not limited to, compressed air, water orwater-based solutions, oil or oil-based solutions, or refrigerants,including, but not limited to, class 1, class 2, or class 3refrigerants. Further exemplary refrigerants may include, but are notlimited to, a supercritical fluid including, but not limited to, carbondioxide, water, methane, ethane, propane, ethylene, propylene, methanol,ethanol, acetone, or nitrous oxide, or combinations thereof. Stillexemplary refrigerants may include, but are not limited to, halon,perchloroolefin, perchlorocarbon, perfluoroolefin, perfluororcarbon,hydroolefin, hydrocarbon, hydrochloroolefin, hydrochlorocarbon,hydrofluoroolefin, hydrofluorocarbon, hydrochloroolefin,hydrochlorofluorocarbon, chlorofluoroolefin, or chlorofluorocarbon typerefrigerants, or combinations thereof. Still further exemplaryembodiments of refrigerant may include, but are not limited to,methylamine, ethylamine, hydrogen, helium, ammonia, water, neon,nitrogen, air, oxygen, argon, sulfur dioxide, carbon dioxide, nitrousoxide, or krypton, or combinations thereof.

It should be appreciated that where combustible or flammablerefrigerants are included for the chiller working fluid, variousembodiments of the system A10 may beneficially couple the heater bodyC100, and/or the fuel source, and the chiller assembly A40 in fluidcommunication such that the combustible or flammable working fluid towhich thermal energy is provided at the chiller assembly A40 may furtherbe utilized as the fuel source for generating heating working fluid, andthe thermal energy therewith, to output from the heater body C100 to theengine working fluid at the engine A100.

Various embodiments of the system A10 include control systems andmethods of controlling various sub-systems disclosed herein, such as,but not limited to, the fuel source, the oxidizer source, the coolingfluid source, the heater body C100, the chiller assembly C40, the engineA100, and the load device C092, including any flow rates, pressures,temperatures, loads, discharges, frequencies, amplitudes, or othersuitable control properties associated with the system A10. In oneaspect, a control system for the system A10 defining a power generationsystem is provided. The power generation system includes one or moreclosed cycle engines (such as engine A100), one or more load devicesdefining electric machines (such as load device C092) operativelycoupled to the engine, and one or more energy storage devices incommunication with the electric machines.

The control system can control the closed cycle engine and itsassociated balance of plant to generate a temperature differential, suchas a temperature differential at the engine working fluid relative tothe heating working fluid and the chiller working fluid. Thus, theengine defines a hot side, such as at the expansion chamber A221, and acold side, such as at the compression chamber A222. The temperaturedifferential causes free piston assemblies A1010 to move within theirrespective piston chambers defined at respective piston bodies C700. Themovement of the pistons A1011 causes the electric machines to generateelectrical power. The generated electrical power can be provided to theenergy storage devices for charging thereof. The control system monitorsone or more operating parameters associated with the closed cycleengine, such as piston movement (e.g., amplitude and position), as wellas one or more operating parameters associated with the electricmachine, such as voltage or electric current. Based on such parameters,the control system generates control commands that are provided to oneor more controllable devices of the system A10. The controllable devicesexecute control actions in accordance with the control commands.Accordingly, the desired output of the system A10 can be achieved.

Furthermore, the control system can monitor and anticipate load changeson the electric machines and can control the engine A100 to anticipatesuch load changes to better maintain steady state operation despitedynamic and sometimes significant electrical load changes on theelectric machines. A method of controlling the power generation systemis also provided. In another aspect, a control system for a heat pumpsystem is provided. The heat pump system includes one or more of theclosed cycle engines described herein. A method of controlling the heatpump system is also provided. The power generation and heat pump systemsas well as control methods therefore are provided in detail herein.

Referring now to FIG. 2, exemplary embodiments of the system A10 arefurther provided. FIG. 2 is an exemplary cross sectional view of thesystem A10 including the heater body C100 and the chiller assembly A40each in thermal communication with the engine A100, or particularly theengine working fluid within the engine A100, such as shown and describedaccording to the schematic block diagram of FIG. 1. The system A10includes a closed cycle engine A100 including a piston assembly A1010positioned within a volume or piston chamber C112 (FIG. 11A and FIG.11B) defined by a wall defining a piston body C700. The volume withinthe piston body C700 is separated into a first chamber, or hot chamber,or expansion chamber A221 and a second chamber, or cold chamber(relative to the hot chamber), or compression chamber A222 by a pistonA1011 of the piston assembly A1010. The expansion chamber A221 ispositioned thermally proximal to the heater body C100 relative to thecompression chamber A222 thermally distal to the heater body C100. Thecompression chamber A222 is positioned thermally proximal to the chillerassembly A40 relative to the expansion chamber A221 thermally distal tothe chiller assembly A40.

In various embodiments, the piston assembly A1010 defines a double-endedpiston assembly A1010 in which a pair of pistons A1011 is each coupledto a connection member A1030. The connection member A1030 may generallydefine a rigid shaft or rod extended along a direction of motion of thepiston assembly A1010. In other embodiments, the connection membersA1030 includes one or more springs or spring assemblies, such as furtherprovided herein, providing flexible or non-rigid movement of theconnection member A1030. In still other embodiments, the connectionmember A1030 may further define substantially U- or V-connectionsbetween the pair of pistons A1011.

Each piston A1011 is positioned within the piston body C700 such as todefine the expansion chamber A221 and the compression chamber A222within the volume of the piston body C700. The load device c092 isoperably coupled to the piston assembly A1010 such as to extract energytherefrom, provide energy thereto, or both. The load device c092defining an electric machine is in magnetic communication with theclosed cycle engine via the connection member A1030. In variousembodiments, the piston assembly A1010 includes a dynamic member A181positioned in operable communication with a stator assembly A182 of theelectric machine. The stator assembly A182 may generally include aplurality of windings wrapped circumferentially relative to the pistonassembly A1010 and extended along a lateral direction L. In oneembodiment, such as depicted in regard to FIG. 2, the dynamic memberA181 is connected to the connection member A1030. The electric machinemay further be positioned between the pair of pistons A1011 of eachpiston assembly A1010. Dynamic motion of the piston assembly A1010generates electricity at the electric machine. For example, linearmotion of the dynamic member A181 between each pair of chambers definedby each piston A1011 of the piston assembly A1010 generates electricityvia the magnetic communication with the stator assembly A182 surroundingthe dynamic member A181.

Referring to FIG. 2, in various embodiments, the working fluid body C108may further define at least a portion of the expansion chamber A221. Inone embodiment, such as further described herein, the working fluid bodyC108 defines a unitary or monolithic structure with at least a portionof the piston body C700, such as to define at least a portion of theexpansion chamber A221. In some embodiments, the heater body C100further defines at least a portion of the working fluid body C108, suchas to define a unitary or monolithic structure with the working fluidbody C108, such as further described herein.

The engine A100 defines an outer end A103 and an inner end A104 eachrelative to a lateral direction L. The outer ends A103 define laterallydistal ends of the engine A100 and the inner ends 104 define laterallyinward or central positions of the engine A100. In one embodiment, suchas depicted in regard to FIG. 2, the heater body C100 is positioned atouter ends A103 of the system A10. The piston body C700 includes a domestructure A26 at the expansion chamber A221. The expansion chamber domestructure A26 s provides reduced surface area heat losses across theouter end A103 of the expansion chamber A221. In various embodiments,the pistons A1011 of the piston assembly A1010 further include domedpistons A1011 corresponding to the expansion chamber A221 dome. The domestructure A26, the domed piston A1011, or both may provide highercompressions ratios at the chambers A221, A222, such as to improve powerdensity and output.

The chiller assembly A40 is positioned in thermal communication witheach compression chamber A222. Referring to FIG. 2, the chiller assemblyA40 is positioned inward along the lateral direction L relative to theheater body C100. In one embodiment, the chiller assembly A40 ispositioned laterally between the heater body C100 and the load devicec092 along the lateral direction L. The chiller assembly A40 providesthe chiller working fluid in thermal communication with the engineworking fluid at the cold side heat exchanger A42 and/or compressionchamber A222. In various embodiments, the piston body C700 defines thecold side heat exchanger A42 between an inner volume wall A46 and anouter volume wall A48 surrounding at least the compression chamber A222portion of the piston body C700.

In various embodiments, such as depicted in regard to FIG. 2, the loaddevice c092 is positioned at the inner end A104 of the system A10between laterally opposing pistons A1011. The load device c092 mayfurther include a machine body c918 positioned laterally between thepiston bodies C700. The machine body c918 surrounds and houses thestator assembly A182 of the load device c092 defining the electricmachine. The machine body c918 further surrounds the dynamic member A181of the electric machine attached to the connection member A1030 of thepiston assembly A1010. In various embodiments, such as depicted inregard to FIG. 2, the machine body c918 further provides an inner endwall A50 at the compression chamber A222 laterally distal relative tothe expansion chamber A221 dome.

Now referring to FIGS. 3A through 9F, exemplary regenerator bodies c800will be described. The presently disclosed regenerator bodies c800 maydefine part of the heater body c100 and/or an engine c002, such as shownand described in regard to system A10 and engine A100 herein, or furtherherein with reference to FIG. 14. For example, a regenerator body c800may define at least a portion of a monolithic body or a monolithicbody-segment. Such monolithic body or monolithic body-segment may defineat least a portion of the heater body c100 and/or the engine c002.Additionally, or in the alternative, the presently disclosed regeneratorbodies c800 may be provided as a separate component, whether for use inconnection with a heater body c100, an engine c002, or any other settingwhether related or unrelated to a heater body c100 or an engine c002. Itwill be appreciated that an engine c002 and/or a heater body c100 mayinclude any desired number of regenerator bodies c800.

FIG. 3A through 3D show an exemplary regenerator body c800 implementedwithin an exemplary engine c002. The regenerator body c800 may fluidlycommunicate with one or more piston bodies c700. For example, aplurality of working-fluid pathways c110 may provide fluid communicationbetween a regenerator body c800 and a piston body c700. Theworking-fluid pathways c110 may fluidly communicate between a pistonchamber c112 defined by the piston body c700 and a regenerator conduitc1000 defined by the regenerator body c800.

The plurality of working-fluid pathways c110 may extend betweenrespective ones of a plurality of piston chamber apertures c111 andrespective ones of a plurality of regenerator apertures c113. The pistonchamber apertures c111 provide fluid communication between theworking-fluid pathways c110 and the piston chamber c112, and theregenerator apertures c113 provide fluid communication between theworking-fluid pathways c110 and the regenerator conduit c1000. Thepiston chamber apertures c111 may define a first end of theworking-fluid pathways c110 and the regenerator apertures c113 maydefine a second end of the working-fluid pathways c110.

A piston body c700 may define a hot-side c1002 of the piston chamberc112 and a cold side piston chamber c1004. A regenerator conduit c1000may include a hot-side portion c1006 and a cold-side portion c1008. Aplurality of hot-side working-fluid pathways c1010 may provide fluidcommunication between the regenerator body c800 and a first piston bodyc700, such as between the hot-side portion c1006 and the hot-side c1002of the piston chamber c112. A plurality of cold-side working-fluidpathways c1010 may provide fluid communication between the regeneratorbody c800 and a second piston body c700, such as between the cold-sideportion c1008 of the regenerator conduit c1000 and the cold-side c1004of the piston chamber c112.

The first piston body c700 may include a first piston assembly c090disposed therein and/or the second piston body c700 may include a secondpiston assembly c090 disposed therein. Heat may be input (QIN) toengine-working fluid disposed within the hot-side working-fluid pathwaysc1010, such as from a heater body c100 (e.g., FIG. 14) or any othersuitable heat source. Heat may be extracted (Q_(OUT)) fromengine-working fluid disposed within the cold-side working-fluidpathways c1012, such as from a chiller body (not shown) or any othersuitable cooling source. A regenerator body c800 may be disposedadjacent to a piston body c700, such as circumferentially adjacent to apiston body c700. As shown in FIG. 3C, a regenerator body c800 maycircumferentially surround a piston body c700. Alternatively, aregenerator body c800 may be disposed adjacent to a piston body c700. Insome embodiments, a semiannular regenerator body c800 may be disposedcircumferentially adjacent to a piston body c700.

During operation, engine-working fluid flowing from the plurality ofhot-side working-fluid pathways c1010 to the regenerator body c800enters the regenerator conduit c1000. Fluid passing through theregenerator conduit c1000 may flow out of the regenerator body c800 andinto the plurality of cold-side working-fluid pathways c1012. Theregenerator conduit c1000 includes a heat storage medium c1014 disposedtherein. The heat storage medium c1014 may be any suitable thermalenergy storage medium within which heat from the hot-side working-fluidpathways c1010 may be intermittently stored as the engine-working fluidflows from the regenerator body c800 to the cold-side working-fluidpathways c1012. In some embodiments, the heat storage medium c1014 mayinclude a plurality of fin arrays c1016; however, other heat storagemedium may additionally or alternatively be utilized, including sensibleheat storage and/or latent heat storage technologies. Other suitableheat storage medium may include packed beds, include molten salts,miscibility gap alloys, silicon materials (e.g., solid or moltensilicon), phase change materials, and so forth.

The plurality of fin arrays c1016 include an array of high-surface areaheat transfer fins having a thermally conductive relationship withengine-working fluid in the regenerator conduit c1000. As fluid flowsfrom the hot-side working-fluid pathways c1010 into or through theregenerator conduit c1000, heat transfers to the heat storage medium1014 (e.g., the plurality of fin arrays c1016), preserving thermalenergy from being extracted (Q_(OUT)) at the chiller body (not shown) orother suitable cooling source. As fluid flows from the cold-sideworking-fluid pathways c1012 into or through the regenerator conduitc1000, heat transfers from the heat storage medium 1014 (e.g., theplurality of fin arrays c1016) back to the engine-working fluid, therebyreturning thermal energy to the engine-working fluid flowing into thehot-side working-fluid pathways c1010.

Still referring to FIG. 3A, in some embodiments, a heat storage mediumc1014 may include a plurality of fin arrays c1016 adjacently disposedwithin a regenerator conduit c1000. The plurality of fin arrays c1016may be respectively supported by the regenerator conduit c1000 in spacedrelation to one another. The spaced relation of the plurality of finarrays c1016 may define a gap, G c1018 longitudinally separatingadjacent ones of the plurality of fin arrays c1016.

Referring now to FIGS. 4A and 4B, an exemplary regenerator conduitsc1000 will be further described. As shown, an exemplary regeneratorconduit c1000 may include a sidewall c1020, such as an annular sidewallc1020. The sidewall c1020 may circumferentially surround the heatstorage medium c1014, such as the plurality of fin arrays c1016. Asshown in FIG. 4B, in some embodiments, a regenerator conduit c1000 maydefine an annulus. For example, the regenerator conduit c1000 mayinclude a radially outward sidewall c1022 and a radially inward sidewallc1024. The radially outward sidewall c1022 may circumferentiallysurround the heat storage medium c1014, such as the plurality of finarrays c1016. The heat storage medium c1014, such as the plurality offin arrays c1016, may circumferentially surround the radially inwardsidewall c1024. The plurality of fin arrays c1016 may extend from theregenerator conduit c1000. FIG. 5 shows an exemplary heat storage mediumc1014. The heat storage medium shown in FIG. 5 includes a plurality offin arrays c1016, which may correspond to the regenerator body c800shown in FIG. 4A. FIGS. 6A and 6B show another exemplary heat storagemedium c1014, such as a plurality of fin arrays c1016, which maycorrespond to the regenerator body c800 shown in FIG. 4B.

As shown in FIG. 5, the regenerator conduit c100 circumferentiallysurrounding the heat storage medium c1014 (e.g., FIG. 4A) has beenomitted to reveal details of the plurality of fin arrays c1016. Asshown, a plurality of fin arrays c1016 may extend from at least aportion of the regenerator conduit c1000 obliquely towards a hot-sideportion c1006 of the regenerator body c800. The regenerator conduit maybe disposed about a longitudinal axis and the plurality of fin arraysc1016 may be supported by the regenerator conduit at least in part at anoblique angle relative to the longitudinal axis. For example, a firstregion c1026 of the plurality of fin arrays c1016 may extend obliquelyfrom the regenerator conduit c1000 towards the hot-side portion c1006 ofthe regenerator body c800. Alternatively, the plurality of fin arraysc1016 may extent from at least a portion of the regenerator conduitc1000 obliquely towards a cold-side portion c1008 of the regeneratorbody c800. Additionally, or in the alternative, at least a portion ofthe plurality of fin arrays c1016 may extend perpendicularly from atleast a portion of the regenerator conduit c1000. The plurality of finarrays c1016 may be supported by the regenerator conduit c800 at leastin part at a perpendicular angle relative to the longitudinal axis. Forexample, a second region c1028 of the plurality of fin arrays c1016 mayextend perpendicularly from the regenerator conduit c1000.

FIG. 7 shows a side view of the plurality of fin arrays c1016, such asthe fin arrays c1016 shown in FIG. 5 or in FIGS. 6A and 6B. As shown inFIG. 7, adjacent ones of the plurality of fin arrays c1016 may include aproximal fin array c1030 and a distal fin array c1032. The proximal finarray c1030 may have a distal surface c1034 and the distal fin arrayc1032 may have a proximal surface c1036. The distal surface c1034 mayface the proximal surface c1036. The distal surface c1034 may beoriented towards the hot-side portion c1006 of the regenerator body c800and the proximal surface c1036 may be oriented towards a cold-sideportion c1008 of the regenerator body. The regenerator conduit c1000 maycommunicate with at least a portion of the distal surface c1034 and/orat least a portion of the proximal surface c1036 at an oblique angle.The oblique angle may be an acute angle or an obtuse angle. The acuteangle may be from 1 degree to 89 degrees, such as from 10 degrees to 70degrees, such as from 30 degrees to 60 degrees, such as from 40 degreesto 50 degrees. The obtuse angle may be from 91 to 179 degrees, such asfrom 100 to 160 degrees, such as from 120 to 150 degrees, such as from130 to 140 degrees.

In some embodiments, at least some of the plurality of fin arrays c1016may have a distal surface c1034 communicating with the regeneratorconduit c1000 at an acute angle, with the distal surface c1034 orientedtowards a hot-side portion c1006 of the regenerator body c800. Theplurality of fin arrays c1016 may have a proximal surface c1036communicating with the regenerator conduit c1000 at an obtuse angle,with the proximal surface c1036 oriented towards a cold-side portionc1008 of the regenerator body c800. Additionally, or in the alternative,at least some of the plurality of fin arrays c1016 may have a distalsurface c1034 communicating with the regenerator conduit c1000 at anobtuse angle, with the distal surface c1034 oriented towards a hot-sideportion c1006 of the regenerator body c800. The plurality of fin arraysc1016 may have a proximal surface c1036 communicating with theregenerator conduit c1000 at an acute angle, with the proximal surfacec1036 oriented towards a cold-side portion c1008 of the regenerator bodyc800. Further in addition or in the alternative, at least some of theplurality of fin arrays c1016 may have a distal surface c1034 and/or aproximal surface c1036 communicating with the regenerator conduit c1000at an angle perpendicular to the regenerator conduit c1000.

The distal surface c1034 of the proximal fin array c1030 and theproximal surface c1036 of the distal fin array c1032 may define a gap Gc1018. Such a gap G c1018 may longitudinally separate the adjacent onesof the plurality of fin arrays c1016, such as the proximal fin arrayc1030 from the distal fin array c1032. The gap G c1018 may reduce orminimize thermally conductive heat transfer in the longitudinaldirection of the regenerator body c800, for example, by separatingrespective ones of the plurality of fin arrays c1016 from one another.The gap G c1018 may longitudinally separate adjacent ones of theplurality of fin arrays c1016 by a longitudinal distance of from about10 microns to about 1 millimeter, such as from about 10 microns to about100 microns, such as from about 100 microns to about 500 microns, orsuch as from about 500 microns to about 1 millimeter. The gap G c1018may be at least 10 microns, such as at least 100 microns, such as atleast 500 microns, such as at least 1 millimeter. The gap G c1018 may beless than 1 millimeter, such as less than 500 microns, such as less than100 microns, such as less than 10 microns. In some embodiments, the gapG c1018 may be selected so as to be at least a thick as a boundary layerof engine-working fluid deposed between the engine-working fluid and thesurface of respective ones of the plurality of fin arrays. Such aboundary layer may isolate adjacent ones of the plurality of fin arraysc1016 from one another.

Referring again to FIG. 3A, in some embodiments, a regenerator body c800may include a hot-side portion c1006 and a cold-side portion c1008. Thehot-side portion c1006 may be operably coupled and fluidly communicatewith the cold-side portion c1008. The hot-side portion c1006 of theregenerator body c800 may include a hot-side regenerator conduit c1038and a hot-side plurality of fin arrays c1040 adjacently disposed withinthe hot-side regenerator conduit c1038 in spaced relation to oneanother. The cold-side portion c1008 of the regenerator body c800 mayinclude a cold-side regenerator conduit c1042 and a cold-side pluralityof fin arrays c1044 adjacently disposed within the cold-side regeneratorconduit c1042 in spaced relation to one another.

The hot-side portion c1006 and the cold-side portion c1008 of theregenerator body c800 may be separated by a hot-to-cold gap H-C c1038.For example, in some embodiments, the spaced relation (e.g., thehot-to-cold gap H-C c1046) of the hot-side plurality of fin arrays c1040to the cold-side plurality of fin arrays c1044 may define a hot-to-coldgap H-C c1038 longitudinally separating the hot-side plurality of finarrays c1040 from the cold-side plurality of fin arrays c1042.Additionally, or in the alternative, the hot-side regenerator conduitc1038 and the cold-side regenerator conduit c1042 may be in the spacedrelation to one another, further defining the hot-to-cold gap H-C c1046.The hot-to-cold gap H-C c1046 may reduce or minimize thermallyconductive heat transfer between the hot-side portion c1006 and thecold-side portion c1008 of the regenerator body c800. In someembodiments, the hot-to-cold gap H-C c1046 may allow a regenerator bodyc800 to provide at least two thermally distinct thermal storage bodieswithin the same regenerator body c800.

In some embodiments, a fin array may define a lattice c1048. The latticec1048 may include a plurality of lattice walls c1050 defining polyhedralpassages c1052 therebetween. Such lattice walls c1050 and polyhedralpassages c1052 as shown, for example, in FIGS. 4A and 4B. Theregenerator conduit c1000 may be disposed about a longitudinal axis Ac204, and the lattice walls c1050 may be oriented parallel to thelongitudinal axis A c204. The polyhedral passages c1052 may have apolygonal cross-section. By way of example, the polyhedral passagesc1050 may have a shape such as a rhombohedron, a right prism, an obliqueprism, a frustum, or a cylinder, as well as combinations of these.

Now turning to FIGS. 8A through 8D, exemplary fin arrays c1016 will befurther described. As shown, in some embodiments, a fin array c1016 mayinclude a plurality of fin supports c1054 and a plurality of fins c1056together defining an array of interconnected fins c1056 and fin supportsc1054. The interconnected fins c1056 and fin supports c1054 may define alattice c1048 as described herein. A plurality of fin supports c1054 maybe disposed laterally and a plurality of fins c1056 may be disposedbetween adjacent ones of the laterally disposed fin supports c1054. Insome embodiments, the plurality of fin supports c1054 may extendobliquely from the regenerator conduit c1000. The regenerator conduitc1000 may be disposed about a longitudinal axis A c204 and the pluralityof fin supports c1054 may be supported by the regenerator conduit c1000at least in part at an oblique angle relative to the longitudinal axis Ac204. As shown, the oblique angle may be oriented towards a hot-sideportion c1006 of the regenerator body c800. Alternatively, the obliqueangle may be oriented towards a cold-side portion c1008 of theregenerator body c800.

The fin supports c1054 may have a distal surface c1034 communicatingwith the regenerator conduit c1000 at an acute angle, with the distalsurface c1034 oriented towards a hot-side portion c1006 of theregenerator body c800. The fin supports c1054 may have a proximalsurface c1036 communicating with the regenerator conduit c1000 at anobtuse angle, with the proximal surface c1036 oriented towards acold-side portion c1008 of the regenerator body c800. Additionally, orin the alternative, at least some of the fin supports c1054 may have adistal surface c1034 communicating with the regenerator conduit c1000 atan obtuse angle, with the distal surface c1034 oriented towards ahot-side portion c1006 of the regenerator body c800. The fin supportsc1054 may have a proximal surface c1036 communicating with theregenerator conduit c1000 at an acute angle, with the proximal surfacec1036 oriented towards a cold-side portion c1008 of the regenerator bodyc800. Further in addition or in the alternative, at least some of thefin supports c1054 may have a distal surface c1034 and/or a proximalsurface c1036 communicating with the regenerator conduit c1000 at anangle perpendicular to the regenerator conduit c1000.

The regenerator conduit c1000 may communicate with at least a portion ofthe fin supports c1054 (e.g., a distal surface c1034 and/or a proximalsurface c1036 thereof) at an oblique angle. The oblique angle may be anacute angle or an obtuse angle. The acute angle may be from 1 degree to89 degrees, such as from 10 degrees to 70 degrees, such as from 30degrees to 60 degrees, such as from 40 degrees to 50 degrees. The obtuseangle may be from 91 to 179 degrees, such as from 100 to 160 degrees,such as from 120 to 150 degrees, such as from 130 to 140 degrees.

In some embodiments, at least a portion of the plurality of fins c1056may extend perpendicularly from the regenerator conduit c1000. Forexample, the regenerator conduit c1000 may be disposed about alongitudinal axis A c204 and the plurality of fins c1056 may besupported at least in part by the regenerator conduit c1000 at aperpendicular angle relative to the longitudinal axis A c204.Additionally, or in the alternative, the plurality of fins c1056 may besupported at least in part by the fin supports c1054 at a perpendicularangle relative to the longitudinal axis A c204.

The plurality of fins c1056 may extend from the plurality of finsupports c1054, such as along the longitudinal axis c204. In someembodiments, the fins c1056 may have a chevron shape. The chevron shapemay include a tip c1058 oriented towards a hot-side portion c1006 of theregenerator body c800 and/or a tail c1060 oriented towards a cold-sideportion c1008 of the regenerator body c800.

While the fins c1056 may extend from the plurality of fin supportsc1054, a gap G c1018 may longitudinally separate adjacent fins c1056and/or fin supports c1054 respectively corresponding to adjacent finarrays c1016. For example, the gap G 1018 may longitudinally separatethe tips c1058 of a proximal fin array c1030 from the tails c1060 of adistal fin array c1032.

As described herein, at least a portion of a regenerator body c800 maydefine an additively manufactured monolithic body or an additivelymanufactured monolithic body-segment. The regenerator body c800 maydefine a portion of a larger monolithic body or monolithic body segment,or the regenerator body c800 may define a module insertable into amonolithic body or a monolithic body-segment. In some embodiments, theplurality of fin arrays c1016 may be monolithically integrated with theregenerator conduit c100. For example, the array of interconnected finsc1056 and fin supports c1058 may define a monolithic structure such as aportion of a monolithic body or monolithic body-segment.

A regenerator body c800 may be formed of one or more materials selectedat least in part on one or more thermal storage properties. For example,one or more materials may be selected for a regenerator body c800 basedat least in part on a thermal conductivity and/or a heat capacity of thematerial. In some embodiments, the plurality of fin arrays c1016 mayinclude a first material and the regenerator conduit may include asecond material that differs from the first material. For example, thethermal conductivity of the first material may exceed the thermalconductivity of the second material. Additionally, or in thealternative, the heat capacity of the first material may exceed the heatcapacity of the second material. In some embodiments, the plurality offin arrays c1016 may include a material selected for thermalconductivity and/or the regenerator conduit c1000 may include a materialselected for thermal resistivity. In an exemplary embodiment, theplurality of fin arrays c1016 may include a metal or metal alloy, andthe regenerator conduit c1000 may include a ceramic. In otherembodiments, the regenerator conduit c1000 may additionally oralternatively include a metal or metal alloy, and/or the plurality offin arrays c1016 may include a ceramic.

Exemplary metal or metal alloys may be selected for high thermalconductivity and/or heat capacity properties. Suitable metal or metalalloys may include copper, aluminum, tin, zinc, nickel, chromium,titanium, tellurium, magnesium, and/or iron. In some embodiments, themetal or metal alloy may include a rare earth element. Exemplary copperalloys may include CuSn, CuZn, CuZnAs, CuZnP, CuZnFe, CuZnNi, CuCr,and/or CuTeSn.

Exemplary ceramics may be selected for low thermal conductivity and/orheat capacity properties. Suitable ceramics may include alumina,beryllia, ceria, and/or zirconia. In some embodiments, the ceramic mayinclude a carbide, a boride, a nitride, and/or a silicide.

Now turning to FIGS. 9A-9F, further exemplary regenerator bodies c800will be described. As shown, a regenerator body c800 may include asidewall c1020, such as a sidewall c1020. The sidewall c1020 may includean internal-sidewall c1062 and an external-sidewall c1064. Theinternal-sidewall c10162 and the external-sidewall c1064 may be spacedapart from one another with a voidspace c1066 defined therebetween. Thevoidspace c1066 may provide thermal resistance to heat flow from thesidewall c1020 to structures or environment adjacent to or surroundingthe sidewall c1020. The voidspace c1066 may include an open space, suchas airgap or a vacuum. The voidspace c1066 may include any gas, such asambient air, an inert gas, etc. The voidspace c1066 may additionally oralternatively include any material that provides thermal resistance toheat flow, such as unsintered or partially sintered powder material(e.g., an additive manufacturing powder material), a mesh, athree-dimensional lattice, a porous medium, or the like.

The overall thermal response of a regenerator body c800 may beconfigured based at least in part on the configuration of theregenerator body c800, including the geometric properties and/or thematerial properties of the regenerator body. For example, a regeneratorbody c800 may be configured to provide a high amount of heat transferbetween the regenerator body and an engine-working fluid, while alsoexhibiting a low amount of heat loss from the hot-side to the cold-side.In some embodiments, regenerator efficiency may be improved byincreasing the effective length of the regenerator conduit c1000, suchas by providing a regenerator conduit c1000 with a gradient incross-sectional area and/or by providing sidewalls c1020 with a gradientin wall thickness, and/or material density or porosity. The gradient maybe oriented along a longitudinal axis and/or a radial axis of theregenerator conduit c1000. Additionally, or in the alternative,regenerator efficiency may be improved by augmenting the configurationand/or composition of the heat storage medium c1014 in the regeneratorconduit c1000. For example, the heat storage medium c1014 may includematerial (such as fin arrays c1016) with a gradient in thickness and/orsurface area and/or material porosity. Regenerator efficiency mayadditionally or alternatively be improved by augmenting an interfacebetween the regenerator conduit c100 and the heat storage medium c1014.

In some embodiments, a regenerator body c800 may include a sidewallc1020, a regenerator conduit c1000, and a heat storage medium c1014disposed within the regenerator conduit c800. The sidewall c1020 mayhave a gradient in gradient in cross-sectional thickness and/or materialthickness oriented along a longitudinal axis of the regenerator conduitc1000. Additionally, or in the alternative, the sidewall c1020 may havea gradient in surface area, and/or material density or porosity,oriented along a longitudinal axis and/or a radial axis of theregenerator conduit c1000. The regenerator conduit c1000 may have agradient in cross-sectional thickness and/or material thickness orientedalong a longitudinal axis of the regenerator conduit c1000.Additionally, or in the alternative, the regenerator conduit c1000 mayhave a gradient in surface area, and/or material density or porosity,oriented along a longitudinal axis and/or a radial axis of theregenerator conduit c1000. The heat storage medium c1014 may have agradient in cross-sectional thickness, material thickness, surface area,and/or material density or porosity, oriented along a longitudinal axisof the regenerator conduit c1000. By way of example, a heat storagemedium that includes a plurality of fin arrays c1016 may include agradient in one or more properties of respective fins and/or fin arraysin the plurality of fins arrays. Such gradient may include a gradient indimensions (e.g., size and/or material thickness of a fin and/or finarray), material density or porosity (e.g., density or porosity of a finand/or fin array), quantity (e.g., quantity of fins in a fin arrayand/or quantity of fin arrays per unit area and/or unit length of theregenerator conduit c1000). It will be appreciated that the respectivegradients described herein may be oriented in any desirable direction orcombination of directions. Additionally, or in the alternative,different gradients may be combined with one another, each which beingoriented in any respective desired direction or combination ofdirections, including different directions from one another.

The transfer of heat between a regenerator body c800 and engine-workingfluid flowing through the regenerator conduit c1000, such as betweenengine-working fluid flowing through the regenerator conduit and theheat storage medium c1014 and/or the sidewalls c1020 (and/or between theheat storage medium c1014 and the sidewalls c1020) is generallyproportional to the heat flux (q=hΔT) at respective areas or points ofheat transfer. While the heat flux may vary under transient conditions,the heat transfer properties of a regenerator body c800 or a portionthereof may be described by a heat transfer time-constant, τ (tau),which has units of seconds, according to the following equation:τ=ρc_(p)V/hA, where ρ is density, c_(p) is the heat capacity, Vis volumeof the body, h is the heat transfer coefficient, and A is the surfacearea. According to the heat transfer time-constant, larger masses (p V)and larger heat capacities (c_(p)) lead to slower changes intemperature, whereas larger surface areas (A) and better heat transfer(h) lead to faster temperature changes.

One or more portions of a regenerator body c800 may be configured toprovide a desired heat transfer time-constant (τ). One or more portionsof a regenerator body c800 may be configured with a time-constant (τ)selected based at least in part on the expected heat flux (q=hΔT) asbetween the one or more portions of the regenerator body c800 andengine-working fluid flowing through the regenerator body c800 undergiven operating conditions. Additionally, or in the alternative, the oneor more regions of the regenerator body c800 may be configured with atime-constant (τ) selected based at least in part on the expected heatflux (q=hΔT) as between the one or more regions of the regenerator bodc800 under given operating conditions. Given a heat transfertime-constant and an initial temperature difference (ΔT_(i)), the totalenergy transfer Q can be described by the equation:

Q=∫ ₀ ^(t) qdt=hA∫ ₀ ^(t) θdt=(pVc _(p))ΔT _(i)└1−e ^(−t/τ)┘.

In some embodiments, a regenerator body c800 may include one or moregeometric parameters and/or one or more material properties that differas between one or more portions of the regenerator body c800 and/or thatvary and/or change across a portion of the regenerator body c800. Suchgeometric parameters and/or material properties may be configured toprovide a desired heat transfer time-constant (τ) for one or morerespective portions of the regenerator body c800. A first regeneratorbody-portion c1068 (such as a hot-side portion c1006) may have a firstheat transfer time-constant (τ₁) and a second regenerator body-portionc1070 (such as a cold-side portion c1008) may have a second heattransfer time-constant (τ₂). Such geometric parameters and/or materialproperties may be selected at least in part to provide a first heattransfer time-constant (τ₁) corresponding to the first regeneratorbody-portion c1068 and/or a second heat transfer time-constant (τ₂)corresponding to the second regenerator body-portion c1070 that differfrom one another. Additionally, and/or in the alternative, one or moreportions of a regenerator body c800 may have a heat transfertime-constant gradient (Δτ) across the respective one or more portionsof the regenerator body. The heat transfer time-constant gradient (Δτ)may be oriented along a longitudinal axis of a regenerator conduitc1000, a radial axis of the regenerator conduit c1000, and/or an axiscorresponding to one or more of a plurality of fin arrays c1016 disposedwithin the regenerator conduit c1000.

In some embodiments, the first regenerator body-portion c1068 and thesecond regenerator body-portion c1070 may have congruent heat transfertime-constants (τ_(c)) as between one another. Additionally, or in thealternative, one or more portions of a regenerator body c800 may have acongruent heat transfer time-constant gradient (Δτ_(c)). Such congruentheat transfer time-constants (τ_(c)) and/or such a congruent heattransfer time-constant gradient (Δτ_(c)) may be attributable at least inpart to one or more geometric parameters and/or one or more materialproperties that differ as between one or more portions of theregenerator body c800 and/or that vary and/or change across a respectiveportion of the regenerator body c800.

As described herein, respective portions of a regenerator body c800 areconsidered to have congruent heat transfer time-constants (τ_(c)) when adifference in heat flux (q₁−q₂) corresponding to the respective heattransfer time-constants (τ) is less than would be the case if not forone or more geometric parameters, and/or one or more materialproperties, that differ as between the respective portions of theregenerator body c800. For example, one or more geometric propertiesand/or one or more material properties may differ as between a hot-sideportion c1006 and a cold-side portion c1008 of a regenerator body c800such that the hot-side portion c1006 and the cold-side portion c1008 areconsidered to have congruent heat transfer time-constants (τ_(c)),because a difference in heat flux (q_(hot)−q_(cold)) as between thehot-side portion c1006 and the cold-side portion c1008 is less thanwould be the case if not for one or more geometric parameters, and/orone or more material properties, being configured to differ as betweenthe hot-side portion c1006 and the cold-side portion c1008.

In some embodiments, a regenerator body c800 may have congruent heattransfer time-constants (τ) in which a difference in heat flux betweenthe hot-side portion c1006 and the cold-side portion c1008(q_(hot)−q_(cold)) is 30% or less, such as 20% or less, such as 10% orless, such as 5% or less, or such as 1% or less, with an engine-workingfluid entering the hot-side portion c1006 at 900 C and theengine-working fluid entering the cold-side portion c1008 at 90 C.Helium may be utilized as the engine-working fluid. The respective heattransfer time-constants (τ) of the hot-side portion c1006 and thecold-side portion c1008 may be determined at respective midpoints of thehot-side portion c1006 and the cold-side portion c1008. Additionally, orin the alternative, the respective heat transfer time-constants (τ) ofthe hot-side portion c1006 and the cold-side portion c1008 may bedetermined by integrating a heat transfer time-constant (τ) across alongitudinal axis of a regenerator conduit c1000, a radial axis of theregenerator conduit c1000, and/or an axis corresponding to one or moreof a plurality of fin arrays c1016 disposed within the regeneratorconduit c1000. The heat flux of the hot-side portion c1006 and thecold-side portion c1008 may be determined from a temperature difference(ΔT) at respective midpoints of the hot-side portion c1006 and thecold-side portion c1008. Additionally, or in the alternative, respectiveheat flux may be determined by integrating a temperature difference (ΔT)across a longitudinal axis of a regenerator conduit c1000, a radial axisof the regenerator conduit c1000, and/or an axis corresponding to one ormore of a plurality of fin arrays c1016 disposed within the regeneratorconduit c1000.

As described herein, a portion of a regenerator body c800 is consideredto have a congruent heat transfer time-constant gradient (Δτ_(c)) when aheat flux gradient (Δq/l) across the respective portion of theregenerator body c800 is less than would be the case if not for one ormore geometric parameters, and/or one or more material properties, thatvary and/or change across the respective portion of the regenerator bodyc800. For example, one or more geometric properties and/or one or morematerial properties may vary and/or change across a hot-side portionc1006 of a regenerator body c800 such that the hot-side portion c1006 isconsidered to have congruent heat transfer time-constant gradient(Δτ_(c)) because a heat flux gradient (Δq/l) across the hot-side portionc1006 is less than would be the case if not for the one or moregeometric parameters, and/or the one or more material properties, beingconfigured to vary and/or change across the hot-side portion c1006. Asanother example, one or more geometric properties and/or one or morematerial properties may vary and/or change across a cold-side portionc1008 of a regenerator body c800 such that the cold-side portion c1008is considered to have congruent heat transfer time-constant gradient(Δτ_(c)) because a heat flux gradient (Δq/l) across the cold-sideportion c1008 is less than would be the case if not for the one or moregeometric parameters, and/or the one or more material properties, beingconfigured to vary and/or change across the cold-side portion c1008. Acongruent heat transfer time-constant gradient (Δτ_(c)) may be orientedalong a longitudinal axis of a regenerator conduit c1000, a radial axisof the regenerator conduit c1000, and/or an axis corresponding to one ormore of a plurality of fin arrays c1016 disposed within the regeneratorconduit c1000.

In some embodiments, a portion of a regenerator body c800 may have acongruent heat transfer time-constant gradient (Δτ_(c)) in which a heatflux gradient (Δq/l) is 0.3 or less, such as 0.2 or less, such as 0.1 orless, such as 0.05 or less, or such as 0.01 or less, with anengine-working fluid entering the hot-side portion c1006 at 900 C andthe engine-working fluid entering the cold-side portion c1008 at 90 C.Helium may be utilized as the engine-working fluid. The heat transfertime-constant gradient (Δτ_(c)) may be determined from a plurality ofpoints across the respective portion of the regenerator body c800.Additionally, or in the alternative, the heat transfer time-constantgradient (Δτ_(c)) may be determined by integrating a heat transfertime-constant (τ) across a longitudinal axis of a regenerator conduitc1000, a radial axis of the regenerator conduit c1000, and/or an axiscorresponding to one or more of a plurality of fin arrays c1016 disposedwithin the regenerator conduit c1000. The heat flux gradient (Δq/l) maybe determined from a temperature gradient (ΔT/l) across the respectiveportion of the regenerator body c800. Additionally, or in thealternative, the heat flux gradient (Δq/l) may be determined byintegrating a temperature gradient (ΔT/l) across a longitudinal axis ofa regenerator conduit c1000, a radial axis of the regenerator conduitc1000, and/or an axis corresponding to one or more of a plurality of finarrays c1016 disposed within the regenerator conduit c1000.

In some embodiments, as shown, for example, in FIG. 9A, a regeneratorbody c800 may have substantially uniform geometry as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008). The regenerator body c800 may include a sidewall c1020 asubstantially uniform cross-sectional thickness as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008). Additionally, or in the alternative, a regenerator body c800 mayinclude a regenerator conduit c1000 and/or a heat storage medium c1014that has a substantially uniform cross-sectional thickness as betweenthe first regenerator body-portion c1068 and the second regeneratorbody-portion c1070. The heat storage medium c1014 may have asubstantially uniform configuration, such as a substantially uniformlattice c1048, as between at least part of the first regeneratorbody-portion c1068 (such as a hot-side portion c1006) and at least partof the second regenerator body-portion c1070 (such as a cold-sideportion c1008).

In some embodiments, as shown, for example, in FIGS. 9B-9F, aregenerator body c800 may have one or more geometric parameters thatdiffer and/or vary as between a first regenerator body-portion c1068(such as a hot-side portion c1006) and a second regenerator body-portionc1070 (such as a cold-side portion c1008), and/or along a longitudinalaxis extending therebetween. The heat storage medium c1014 may have oneor more geometric parameters that differ and/or vary, such as a latticec1048 with one or more geometric parameters that differ and/or vary, asbetween at least part of the first regenerator body-portion c1068 (suchas a hot-side portion c1006) and at least part of the second regeneratorbody-portion c1070 (such as a cold-side portion c1008). Additionally, orin the alternative, one or more portions of a generator body c800 maydiffer and/or vary in respect of one or more material properties, suchas composition, heat capacity, density, and/or mass, as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008), and/or along a longitudinal axis extending therebetween.

As shown in FIGS. 9B and 9C, a regenerator body c800 may have a sidewallc1020 with at least one aspect that differs and/or varies in respect ofcross-sectional thickness as between a first regenerator body-portionc1068 (such as a hot-side portion c1006) and a second regeneratorbody-portion c1070 (such as a cold-side portion c1008), and/or along alongitudinal axis extending therebetween. The cross-sectional thicknessof the regenerator conduit c1000 and/or the heat storage medium c1014may remain substantially constant as between the first regeneratorbody-portion c1068 to the second regenerator body-portion c1070, and/oralong a longitudinal axis extending therebetween, as shown, for example,in FIGS. 9A-9C.

In some embodiments, the cross-sectional thickness of a sidewall c1020may decrease from a hot-side portion c1006 to a cold-side portion c1008.The decrease in cross-sectional thickness from the hot-side portionc1006 to the cold-side portion c1008 may compensate for differences inthermal conductivity and specific heat of the engine-working fluid atthe as between the hot-side portion c1006 to the cold-side portionc1008. Additionally, or in the alternative, the cross-sectionalthickness of a sidewall c1020 may vary along the longitudinal axis ofthe regenerator conduit c1000, while decreasing from the hot-sideportion c1006 to the cold-side portion c1008. The varyingcross-sectional thickness may reduce heat flux gradient between theregenerator body c800 and the engine-working fluid, along theregenerator conduit c1000 and/or as between the hot-side portion c1006and the engine-working fluid and/or as between the cold-side portionc1008 and the engine-working fluid.

Additionally or in the alternative, as shown in FIGS. 9D-9F, aregenerator body c800 may include a regenerator conduit c1000 and/or aheat storage medium c1014 that differs and/or varies in respect ofcross-sectional thickness as between a first regenerator body-portionc1068 (such as a hot-side portion c1006) and a second regeneratorbody-portion c1070 (such as a cold-side portion c1008), and/or along alongitudinal axis extending therebetween. A regenerator conduit c1000and/or a heat storage medium c1014 may additionally or alternativelydiffer in respect of surface area and/or volume as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008), and/or along a longitudinal axis extending therebetween. Thecross-sectional thickness of the sidewall c1020 may remain substantiallyconstant as between the first regenerator body-portion c1068 to thesecond regenerator body-portion c1070, and/or along a longitudinal axisextending therebetween, as shown, for example, in FIG. 9D. Additionally,or in the alternative, the cross-sectional thickness of the sidewallc1020 may differ and/or vary along a longitudinal axis extending fromthe first regenerator body-portion c1068 to the second regeneratorbody-portion c1070, as shown in FIGS. 9B, 9C, 9E, and 9F. A regeneratorbody c800 may additionally or alternatively differ and/or vary inrespect of external cross-sectional thickness as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008), and/or along a longitudinal axis extending therebetween, asshown in FIGS. 9C-9F.

In some embodiments, the cross-sectional thickness and/or surface areaof the regenerator conduit c1000 and/or the heat storage medium c1014may decrease from a hot-side portion c1006 to a cold-side portion c1008.The decrease in cross-sectional thickness and/or surface area from thehot-side portion c1006 to the cold-side portion c1008 may compensate fordifferences in thermal conductivity and specific heat of theengine-working fluid at the as between the hot-side portion c1006 to thecold-side portion c1008. Additionally, or in the alternative, thecross-sectional thickness and/or surface area of the regenerator conduitc1000 and/or the heat storage medium c1014 may vary along thelongitudinal axis of the regenerator conduit c1000, while decreasingfrom the hot-side portion c1006 to the cold-side portion c1008. Thevarying cross-sectional thickness and/or surface area may reduce heatflux gradient between the regenerator body c800 and the engine-workingfluid, along the regenerator conduit c1000 and/or as between thehot-side portion c1006 and the engine-working fluid and/or as betweenthe cold-side portion c1008 and the engine-working fluid.

By way of example, as shown in FIG. 9B, a regenerator body c800 mayinclude a sidewall c1020 that includes at least one aspect that differsin respect of cross-sectional thickness as between a first regeneratorbody-portion c1068 (such as a hot-side portion c1006) and a secondregenerator body-portion c1070 (such as a cold-side portion c1008). Forexample, the internal-sidewall c1062 may differ in respect ofcross-sectional thickness, as shown. Additionally, or in thealternative, the external sidewall c1064 and/or the voidspace c1066 maydiffer in respect of cross-sectional thickness as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008). The cross-sectional thickness of at least one aspect of thesidewall c1020 may decrease along a longitudinal axis extending from thefirst regenerator body-portion c1068 to the second regeneratorbody-portion c1070, as shown. Additionally, or in the alternative, thecross-sectional thickness of at least one aspect of the sidewall c1020may increase along a longitudinal axis extending from the firstregenerator body-portion c1068 to the second regenerator body-portionc1070.

In some embodiments, the cross-sectional thickness of the sidewall c1020may remain substantially constant along a longitudinal axis extendingfrom the first regenerator body portion c1068 to the second regeneratorbody portion c1070, while the internal-sidewall c1062 differs in respectof cross-sectional thickness along the longitudinal axis. Thecross-sectional thickness of the internal sidewall c1062 and thecross-sectional thickness of the voidspace c1066 may differ inverselyfrom one another along the longitudinal axis. The cross-sectionalthickness of the internal sidewall c1062 may decrease along thelongitudinal axis, while the cross-sectional thickness of the voidspacec1066 may increase along the longitudinal axis. The cross-sectionalthickness of the regenerator conduit c1000 and/or the heat storagemedium c1014 may remain substantially constant along the longitudinalaxis while at least one aspect of the sidewall c1020 varies in respectof cross-sectional thickness.

As shown in FIG. 9C, in some embodiments a regenerator body c800 mayadditionally or alternatively include a sidewall c1020 with at least oneaspect that varies in respect of cross-sectional thickness along alongitudinal axis extending from the first regenerator body-portionc1068 (such as a hot-side portion c1006) to the second regeneratorbody-portion c1070 (such as a cold-side portion c1008). For example, atleast one aspect of the sidewall c1020 may include a plurality ofalternating changes in cross-sectional thickness along the longitudinalaxis. As shown, the internal-sidewall c1062 may vary in respect ofcross-sectional thickness along the longitudinal axis, such as with aplurality of alternating changes in cross-sectional thickness along thelongitudinal axis. Additionally or alternatively, the external sidewallc1064 and/or the voidspace c1066 may vary in respect of cross-sectionalthickness along the longitudinal axis, such as with a plurality ofalternating changes in cross-sectional thickness along the longitudinalaxis. The external cross-sectional thickness of the regenerator bodyc800 may additionally or alternatively vary in respect ofcross-sectional thickness along the longitudinal axis, such as with aplurality of alternating changes in cross-sectional thickness along thelongitudinal axis, as shown in FIG. 9C. The cross-sectional thickness ofthe regenerator conduit c1000 and/or the heat storage medium c1014 mayremain substantially constant along the longitudinal axis while at leastone aspect of the sidewall c1020 varies in respect of cross-sectionalthickness.

As shown in FIG. 9D, in some embodiments a regenerator body c800 includea regenerator conduit c1000 and/or a heat storage medium c1014 with atleast one aspect that differs in respect of cross-sectional thickness asbetween a first regenerator body-portion c1068 (such as a hot-sideportion c1006) and the second regenerator body-portion c1070 (such as acold-side portion c1008), and/or along a longitudinal axis therebetween.The cross-sectional thickness of the sidewall c1020 may remainsubstantially constant as between the first regenerator body-portionc1068 to the second regenerator body-portion c1070, and/or along alongitudinal axis extending therebetween.

As shown in FIG. 9E, in some embodiments a regenerator body c800 may aregenerator conduit c1000 and/or a heat storage medium c1014 with atleast one aspect that differs in respect of cross-sectional thickness,and a sidewall c1020 that includes at least one aspect that differs inrespect of cross-sectional thickness, as between a first regeneratorbody-portion c1068 (such as a hot-side portion c1006) and the secondregenerator body-portion c1070 (such as a cold-side portion c1008),and/or along a longitudinal axis therebetween. For example, as between afirst regenerator body-portion c1068 and a second regeneratorbody-portion c1070. the internal-sidewall c1062 may differ in respect ofcross-sectional thickness, and the regenerator conduit c1000 and/or theheat storage medium c1014 may differ in respect of cross-sectionalthickness. Additionally, or in the alternative, the external sidewallc1064 and/or the voidspace c1066 may differ in respect ofcross-sectional. The cross-sectional thickness of at least one aspect ofthe sidewall c1020, and the cross-sectional thickness of the regeneratorconduit c1000 and/or the heat storage medium c1014, may decrease along alongitudinal axis extending from the first regenerator body-portionc1068 to the second regenerator body-portion c1070, as shown.Additionally, or in the alternative, the cross-sectional thickness of atleast one aspect of the sidewall c1020, and the cross-sectionalthickness of the regenerator conduit c1000 and/or the heat storagemedium c1014, may increase along a longitudinal axis extending from thefirst regenerator body-portion c1068 to the second regeneratorbody-portion c1070

As shown in FIG. 9F, in some embodiments a regenerator body c800 mayinclude a sidewall c1020, and regenerator conduit c1000 and/or the heatstorage medium c1014, a with at least one aspect that varies in respectof cross-sectional thickness along a longitudinal axis extending fromthe first regenerator body-portion c1068 (such as a hot-side portionc1006) to the second regenerator body-portion c1070 (such as a cold-sideportion c1008). For example, at least one aspect of the sidewall c1020,and at least one aspect of the regenerator conduit c1000 and/or the heatstorage medium c1014, may include a plurality of alternating changes incross-sectional thickness along the longitudinal axis. As shown, theoverall cross-sectional thickness of the sidewall c1062 may remainsubstantially constant in respect of cross-sectional thickness along thelongitudinal axis, while the external cross-sectional thickness of theregenerator body c800 decreases and/or varies as between a firstregenerator body-portion c1068 (such as a hot-side portion c1006) and asecond regenerator body-portion c1070 (such as a cold-side portionc1008), and/or along a longitudinal axis extending therebetween.

These and other embodiments exhibiting differing and/or variablegeometric parameters, and/or differing and/or varying materialproperties, may be configured to provide a desired heat transfertime-constant (τ), such as a congruent heat transfer time-constant (τ),as between at least part of the first regenerator body-portion c1068(such as a hot-side portion c1006) and at least part of the secondregenerator body-portion c1070 (such as a cold-side portion c1008).

Now turning to FIG. 10, exemplary methods of regenerating heat in anengine-working fluid will be described. The exemplary methods ofregenerating heat in an engine-working fluid may be performed inconnection with operation of a regenerator body c800, a heater bodyc100, and/or an engine c002 as described herein. As shown in FIG. 10, anexemplary method c1080 may include, at block c1084, flowing anengine-working fluid from a hot-side portion c1006 of a regenerator bodyc800 towards a cold-side portion of the regenerator body c1008. Theregenerator body c800 may include a regenerator conduit c1000 and aplurality of fin arrays c1016 adjacently disposed within the regeneratorconduit c1000. The exemplary method c1080 may include, at block c1084,transferring heat from the engine-working fluid to the plurality of finarrays c1016. The plurality of fin arrays c1016 may be respectivelysupported by the regenerator conduit c1000 in spaced relation to oneanother. The spaced relation of the plurality of fin arrays c1016 maydefine a gap G 1018 longitudinally separating adjacent ones of theplurality of fin arrays c1016. The exemplary method c1080 may furtherinclude, at block c1086, flowing the engine-working fluid from thecold-side portion c1008 of the regenerator body c800 towards thehot-side portion c1006 of the regenerator body c800. At block c1088, theexemplary method c1080 may include transferring heat from the pluralityof fin arrays c1016 to the engine-working fluid.

In some methods c1080, flowing the engine-working fluid from thehot-side portion c1006 of the regenerator body c800 may include, atblock c1090, flowing the engine-working fluid from a plurality ofhot-side working-fluid pathways c1010 into the regenerator conduitc1000. The plurality of hot-side working-fluid pathways c1010 mayfluidly communicate with the hot-side portion c1006 of the regeneratorbody c800. Exemplary methods c1080 may additionally or alternativelyinclude, at block c1092, flowing the engine-working fluid from ahot-side c1002 of the piston chamber c112 into the plurality of hot-sideworking-fluid pathways c1010. The hot-side c1002 of the piston chamberc112 may fluidly communicate with the plurality of hot-sideworking-fluid pathways c1010.

In some methods c1080, flowing the engine-working fluid from thecold-side portion c1008 of the regenerator body c800 may include, atblock c1094, flowing the engine-working fluid from a plurality ofcold-side working-fluid pathways c1012 into the regenerator conduitc1000. The plurality of cold-side working-fluid pathways c1012 mayfluidly communicate with the cold-side portion c1008 of the regeneratorbody c800. Exemplary methods c1080 may additionally or alternativelyinclude, at block c1096, flowing the engine-working fluid from acold-side c1004 of the piston chamber c112 into the plurality ofcold-side working-fluid pathways c1012. The cold-side c1004 of thepiston chamber c112 may fluidly communicate with the plurality ofcold-side working-fluid pathways c1012.

In some embodiments, an exemplary method c1080 may include transferringa first quantity of heat per unit area from the engine-working fluid tothe plurality of fin arrays c1016 while transferring a second quantityof heat per unit area from the engine-working fluid to the regeneratorconduit c1000. The first quantity of heat per unit area may exceed thesecond quantity of heat per unit area. The plurality of fin arrays c1016may include a first material and the regenerator conduit c1000 mayinclude a second material. The thermal conductivity and of the firstmaterial may exceed the thermal conductivity of the second material.Additionally, or in the alternative, the heat capacity of the firstmaterial may exceed the heat capacity of the second material.

Exemplary conduction-enhancing protuberances may include any one or moreof a combination of protuberant features having a variety of shapes andconfigurations, including nodules, loops, hooks, bumps, burls, clots,lumps, knobs, projections, protrusions, swells, enlargements,outgrowths, accretions, blisters, juts, and the like. Theseconduction-attenuating protuberances c728 occur in an ordered,semi-ordered, random, or semi-random fashion. However, the particularconfiguration, arrangement, or orientation of the conduction-enhancingprotuberances c728 may be selectively controlled or modified byadjusting the configuration or arrangement of at least a portion of theworking-fluid body c108 and/or hot-side heat exchanger body c600, suchas the configuration or arrangement of at least a portion of theworking-fluid pathways c110 and/or heating fluid pathways c602.

It should be appreciated that in various embodiments the surface areawithin the heater conduits or working-fluid pathways C110 corresponds toan internal wall or surface of the heater conduit C110 at which theengine working fluid is in direct contact. In one embodiment, thesurface area defines a nominal surface area of the working-fluid pathwayC110, such as a cross sectional area within the working-fluid pathwayC110. In other embodiments, features may be added or altered to theworking-fluid passage C110 within the heater conduit, such as, but notlimited to, surface roughness, protuberances, depressions, spikes,nodules, loops, hooks, bumps, burls, clots, lumps, knobs, projections,protrusions, swells, enlargements, outgrowths, accretions, blisters,juts, and the like, or other raised material, or combinations thereof,to desirably alter flow rate, pressure drop, heat transfer, flow profileor fluid dynamics of the engine working fluid.

Now referring to FIGS. 11A and 11B, exemplary engine assemblies c900will be described. The engine assemblies c900 described herein mayinclude an engine c002, such as described in regard to the system A10and engine A100 shown and depicted in regard to FIG. 1, or furtherherein with reference to FIG. 14. The engine assembly c900 may includeone or more monolithic bodies or monolithic body-segments as describedherein. A monolithic body and/or a monolithic body-segment may befabricated using an additive manufacturing technology and may be void ofany seams, joints, or the like characteristic of separately fabricatedcomponents.

An engine c002 may include one or more heater bodies c100 and one ormore engine bodies c050 that together define an engine assembly c900. Anexemplary engine assembly c900 may include at least one heater body c100and at least one engine body c050. However, it will be appreciated thatany number of heater bodies c100 and/or any number of engine bodies c050may be provided. In some embodiments, a first heater body c100 may bedisposed at a first side of an engine assembly c900 and a second heaterbody c100 may be disposed at a second side of an engine assembly c900.One or more engine bodies c050 may be disposed adjacent to the firstheater body c100 and/or adjacent to the second heater body c100. One ormore heater bodies c100 and/or one or more engine bodies c050 may beoperably coupled or operably couplable to one another such as viawelding, fusing, or the like, so as to provide an integrally formedengine assembly c900. Additionally, or in the alternative, one or moreheater bodies c100 and/or one or more engine bodies c050 may be operablycoupled or operably couplable to one another such as via bolts,fasteners, or the like, so as to provide an assembled engine assemblyc900.

The engine assembly c900 may include one or more piston assemblies c090and one or more generator assemblies c092. The one or more pistonassemblies c090 and the one or more generator assemblies c092 may beoperably insertable within an engine body c050 and/or a heater bodyc100. The one or more generator assemblies c092 may receive a mid-wardportion of the one or more piston assemblies 092. The one or more pistonassemblies c090 and/or the one or more generator assemblies c092 may beinserted into an engine body c050 and/or a heater body c100 prior tooperably coupling at least one engine body c050 to another engine bodyc050 or to a heater body c100. Additionally, or in the alternative, oneor more piston assemblies c090 and/or the one or more generatorassemblies c092 may be inserted into an engine body c050 and/or a heaterbody c100 prior to operably coupling at least one heater body c100 to anengine body c050. In this way, an engine assembly c900 may be integrallyformed and/or assembled at least in part by installing one or morepiston assemblies c090 and/or the one or more generator assemblies c092into one or more monolithic bodies and/or monolithic body-segments thatmake up the engine assembly c900. The one or more monolithic bodiesand/or monolithic body-segments may be operably coupled to one anotherafter having installed the one or more piston assemblies c090 and/or theone or more generator assemblies c092 therein. However, it will beappreciated that in some embodiments some of the more monolithic bodiesand/or monolithic body-segments that make up an engine assembly c900 maybe operably coupled to one another prior to installing the one or morepiston assemblies c090 and/or the one or more generator assemblies c092therein.

FIGS. 11A and 11B show exploded views of exemplary engine assembliesc900. An engine assembly c900 may include at least two monolithic bodiesor monolithic body-segments, within which one or more piston assembliesc090 and one or more generator assemblies c092 may be enclosed. Forexample, an engine assembly c900 may include a first monolithic bodythat includes a first heater body c100 and a first portion of an enginebody c050, and a second monolithic body that includes a second heaterbody c100 and a second portion of an engine body c050. In someembodiments, an engine assembly c900 may include only two monolithicbodies or monolithic body-segments, while in other embodiments an engineassembly c900 may include more than two (e.g., multiple) monolithicbodies or monolithic body-segments.

One or more of the monolithic bodies and/or monolithic body-segmentsthat make up an engine assembly may include one or more regeneratorbodies and/or one or more chiller bodies. The one or more regeneratorbodies may define a portion of another monolithic body or a portion of amonolithic body-segment. Alternatively, the one or more regeneratorbodies may represent a monolithic body or monolithic body-segment, suchas a monolithic body or monolithic body-segment insertable, inserted,operably couplable, or operably coupled to another monolithic body ormonolithic body-segment. The one or more chiller bodies may define aportion of another monolithic body or a portion of a monolithicbody-segment. Alternatively, the one or more chiller bodies mayrepresent a monolithic body or monolithic body-segment, such as amonolithic body or monolithic body-segment insertable, inserted,operably couplable, or operably coupled to another monolithic body ormonolithic body-segment.

As shown in FIG. 11A, an engine assembly c900 may include a plurality ofmonolithic bodies or monolithic body-segments separated at or aboutlocations corresponding to respective components of the engine assembly.Engine assemblies c900 configured in accordance with FIG. 11A mayinclude separate monolithic bodies or monolithic body-segmentsrespectively corresponding to respective elements of the engine assemblyc900. For example, an engine assembly c900 may include a firstmonolithic body-segment (e.g., on the top left-hand side as shown) thatincludes a first heater body c100, a second monolithic body-segment thatincludes a first portion of an engine body c050 corresponding to aleft-hand side of one or more piston assemblies c090, a third monolithicbody-segment that includes a second portion of the engine body c050corresponding to one or more generator assemblies c092, a fourthmonolithic body-segment that includes a third portion of the engine bodyc050 corresponding to a right-hand side of the one or more pistonassemblies c090, and a fifth monolithic body-segment that includes asecond heater body c100. The first monolithic body-segment that includesthe first heater body c100 may additionally include a portion of theengine body c050. Additionally, or in the alternative, the secondmonolithic body-segment that includes the second heater body c100 mayinclude a portion of the engine body c050.

The second monolithic body-segment may define one or more regeneratorbodies and/or one or more chiller bodies corresponding to the firstheater body c100. Additionally, or in the alternative, one or moreregenerator bodies and/or one or more chiller bodies corresponding tothe first heater body c100 may be operably coupled or operably couplableto the second monolithic body-segment. The fourth monolithicbody-segment may define one or more regenerator bodies and/or one ormore chiller bodies corresponding to the second heater body c100.Additionally, or in the alternative, one or more regenerator bodiesand/or one or more chiller bodies corresponding to the second heaterbody c100 may be operably coupled or operably couplable to the fourthmonolithic body-segment.

The one or more generator assemblies c092 may be installed in one ormore generator housing defined by the second portion of the engine bodyc050. A first portion of one or more piston assemblies c090 may beinstalled in a corresponding one or more piston chambers c112 defined bythe first portion of the engine body c050 and/or a second portion of theone or more piston assemblies c090 may be installed in a correspondingone or more piston chambers c112 defined by the second portion of theengine body c050. The respective portions of the engine assembly c900may be operably coupled to one another, enclosing the one or moregenerator assemblies c092 and the one or more piston assemblies c090therein.

In some embodiments, it may be advantageous for the monolithic body ormonolithic body-segment that defines a heater body c100 to also definethe one or more regenerator bodies corresponding to the heater body.When the heater body c100 and corresponding one or more regeneratorbodies respectively define a portion of the same monolithic body ormonolithic body-segment, working-fluid pathways c110 defined by theheater body c110 may fluidly communicate with the corresponding one ormore regenerator bodies while minimizing fluid couplings.

In some embodiments, it may be advantageous for a monolithic body ormonolithic body-segment that defines one or more generator housing toalso define one or more chiller bodies corresponding to the one or moregenerator assemblies c092 respectively corresponding to the one or moregenerator housings. For example, this may allow for cooling fluidpathways to be defined by such monolithic body or monolithicbody-segment while minimizing fluid couplings associated with the one ormore chiller bodies.

The monolithic bodies and/or monolithic body-segments depicted in FIGS.11A and 11B may respectively reflect one or more additively manufacturedmonolithic bodies or additively manufactured monolithic body-segments.In some embodiments a monolithic body or a monolithic body-segment maybe additively manufactured in a continuous process, such as to provide asingle monolithic structure void of any seams, joints, or the likecharacteristic of separately fabricated components. Additionally, or inthe alternative, a monolithic body or a monolithic body-segment mayinclude a plurality of separately fabricated components, which may beformed using an additive manufacturing technology or other suitablefabrication technologies. For example, a heater body c100 and/or anengine c002 may additionally or alternatively include a plurality ofcomponents formed using a fabrication technology other than additivemanufacturing, and such separately components may be operably coupled oroperably couplable to one another and/or to one or more monolithicbodies and/or a monolithic body-segments. Other suitable fabricationtechnologies that may be used to manufacture various components of thepresently disclosed heater bodies c100 and closed-cycle engines c002include, without limitation, forming (e.g., rolling, stamping, joining,etc.), extruding (e.g., sheet extruding), subtractive manufacturing(e.g., machining, drilling, laser cutting, etc.), forging or casting, aswell as a combination thereof, or any other manufacturing technology.

Still referring to FIGS. 11A and 11B, an exemplary engine assembly c900may include a first heater body c902 and a first engine body c904. Anexemplary engine assembly c900 may additionally or alternatively includea second heater body c930 and/or a second engine body c932.

Now referring to FIG. 11A, in some embodiments, an engine assembly c900may include a plurality of monolithic body-segments. For example, asshown in FIG. 11A, an engine assembly may include a first heater bodyc902, a first engine body c904, a second heater body c940, a secondengine body c942, and a third engine body c960. As shown, a first heaterbody c902 may define at least a portion of a first monolithicbody-segment c912. The first engine body c904 may define at least aportion of a second monolithic body-segment c914. The first engine bodyc904 may include a first piston body c916, and the first piston bodyc916 may define at least a portion of the second monolithic body-segmentc914. The first piston body c916 may define at least a portion of apiston chamber c112. The piston chamber c112 may be configured toreceive at least a portion of a piston assembly c090. The secondmonolithic body-segment c914 (e.g., the first piston body c916) may beoperably coupled or operably couplable to the first monolithicbody-segment c912 (e.g., the first heater body c902). For example, thesecond monolithic body-segment c914 (e.g., the first engine body c904)may be operably coupled or operably couplable to the first heater bodyc902.

The first engine body c904 may include a first regenerator body c926and/or a first chiller body c928. The first regenerator body c926 and/orthe first chiller body c928 may define at least a portion of the secondmonolithic body-segment c914. Additionally, or in the alternative, thefirst regenerator body c926 and/or the first chiller body c928 maydefine a monolithic body-segment operably coupled or operably couplableto the first monolithic body c908 or the second monolithic body-segmentc914.

Still referring to FIG. 11A, an exemplary engine assembly c900 mayadditionally or alternatively include a second heater body c930 and/or asecond engine body c932. As shown, a second heater body c930 may defineat least a portion of a fourth monolithic body-segment c940.Additionally, or in the alternative, a second engine body c932 maydefine at least a portion of a fifth monolithic body-segment c942. Asecond piston body c944 may define at least a portion of the fifthmonolithic body-segment c942. The fifth monolithic body-segment c942 maybe operably coupled or operably couplable to the fourth monolithicbody-segment c940. For example, the fifth monolithic body-segment c942(e.g., the second engine body c932 or the second piston body c944) maybe operably coupled or operably couplable to the second heater bodyc930.

The second engine body c932 may include a second regenerator body c952and/or a second chiller body c954. The second regenerator body c952and/or the second chiller body c954 may define at least a portion of thefifth monolithic body-segment c942. Additionally, or in the alternative,the second regenerator body c952 and/or the second chiller body c954 maydefine a monolithic body-segment operably coupled or operably couplableto the second monolithic body c936 or the fifth monolithic body-segmentc942. In some embodiments, the second piston body c944 may include asecond regenerator body c952 and/or a second chiller body c954. Thesecond regenerator body c952 may define a portion of the second pistonbody c944 or at least a portion of a monolithic body-segment operablycoupled or operably couplable to the second piston body c944.Additionally, or in the alternative, the second chiller body c954 maydefine a portion of the second piston body c944 or at least a portion ofa monolithic body-segment operably coupled or operably couplable to thesecond piston body c944.

An exemplary engine assembly c900 may additionally or alternativelyinclude a third engine body c960. The third engine body c960 may includea first machine body c918, and the first machine body c918 may define atleast a portion of a third monolithic body-segment c924. The firstmachine body c918 may define at least a portion of a generator housingc919. The generator housing c919 may be configured to receive at least aportion of a load device c092. The third monolithic body-segment c924(e.g., the first machine body c918) may be operably coupled or operablycouplable to the second monolithic body-segment c914 (e.g., the firstpiston body c916).

Now referring to FIG. 12, an exemplary engine assembly c900 may includea one or more engine-working fluid heat exchanger bodies c988. The oneor more engine-working fluid heat exchanger bodies c988 may define atleast a portion of the first heater body c902 and/or at least a portionof the first engine body c904. A working-fluid heat exchanger body c988may include a plurality of working-fluid pathways c110 fluidlycommunicating between a piston body and a regenerator body (e.g.,between a first piston body c916 and a first regenerator body c926, orbetween a second piston body c944 and a second regenerator body c952).For example, an engine body c904 may include a first piston body c916, afirst regenerator body c926, and a working-fluid heat exchanger bodyc988 that includes a plurality of working-fluid pathways c110 fluidlycommunicating between the first piston body c916 and the firstregenerator body c926. The working-fluid heat exchanger body c988 maydefine at least a portion of the first heater body c902 and/or at leasta portion of the first engine body c904. The working-fluid heatexchanger body c988 may additionally or alternatively include a heatingchamber body c990.

In some embodiments, the first heater body c902 may define at least aportion of a first monolithic-body segment c912 and/or the first enginebody c904 may define at least a portion of a second monolithic-bodysegment c914. The first heater body c902 may include at least a portionof the heating chamber body c990. The heating chamber body c990 maydefine at least a portion of the first monolithic body-segment c912. Thesecond monolithic body-segment c914 may include at least a portion ofthe working-fluid heat exchanger body c988, at least a portion of thefirst piston body c916, and/or at least a portion of the firstregenerator body c926. The working-fluid heat exchanger body c988 maydefine at least a portion of the second monolithic body-segment c914.The heating chamber body c990 may surround at least a portion of theworking-fluid heat exchanger body c988. For example, the heating chamberbody c990 may define at least a portion of a recirculation pathway c104surrounding at least a portion of the working-fluid heat exchanger bodyc988. The heating chamber body c990 may fluidly communicate at anupstream portion (e.g., at a radially inward portion) with a heatingfluid inlet c992. For example, the heating chamber body c990 may fluidlycommunicate with a combustion chamber c102, such as with a combustionchamber outlet c412. The heating chamber body c990 may fluidlycommunicate at a downstream portion (e.g., at a radially outwardportion) with a heating fluid outlet c994. For example, the heatingchamber body c990 may fluidly communicate with a recirculation annulusc208.

Now turning to FIG. 13, exemplary methods of building an engine assemblyc900 will be described. As shown in FIG. 13, an exemplary method c4000may include, at block c4002, coupling a first monolithic body c908 or afirst monolithic body-segment c912 to a second monolithic body c936 or asecond monolithic body segment c914. The first monolithic body c908 orthe first monolithic body-segment c914 may have been additivelymanufactured and/or the second monolithic body c936 or the secondmonolithic body-segment c914 may have been additively manufactured. Thefirst monolithic body c908 or the first monolithic body-segment c912 mayinclude a first heater body c902 and/or a first engine body c904. Thesecond monolithic body c936 or the second monolithic body-segment c914may include a second heater body c930 and/or a second engine body c932.The first monolithic body c908 or the first monolithic body-segment c912may include a first piston assembly c090 and/or a first load device c092installed therein. Additionally, or in the alternative, the secondmonolithic body c936 or the second monolithic body-segment c914 mayinclude the first piston assembly c090 and/or the first load device c092installed therein.

An exemplary method 1000 may include, at block c4004, additivelymanufacturing the first monolithic body c908 or the first monolithicbody-segment c912. Additively manufacturing the first monolithic bodyc908 or the first monolithic body-segment c912 may include additivelymanufacturing the first heater body c902 and/or the first engine bodyc904. An exemplary method 1000 may include, at block c4006, installingthe first piston assembly c090 and/or the first load device c092 in thefirst monolithic body c908 or the first monolithic body-segment c912.For example, the method 1000 may include installing the first pistonassembly c090 in the first heater body c902 and/or in the first enginebody c904. Additionally, or in the alternative, the method 1000 mayinclude installing the first load device c092 in the first heater bodyc902 and/or in the first engine body c904.

An exemplary method 1000 may include, at block c4008, additivelymanufacturing the second monolithic body c936 or the second monolithicbody-segment c914. Additively manufacturing the second monolithic bodyc936 or the second monolithic body-segment c914 may include additivelymanufacturing the second heater body c930 and/or the second engine bodyc932. An exemplary method 1000 may include, at block c4010, installingthe first piston assembly c090 and/or the first load device c092 in thesecond monolithic body c936 or the second monolithic body-segment c914.For example, the method 1000 may include installing the first pistonassembly c090 in the second heater body c930 and/or the second enginebody c932. Additionally, or in the alternative, the method 1000 mayinclude installing the first load device c092 in the second heater bodyc930 and/or the second engine body c932.

An exemplary method 1000 may include, at block c4012, additivelymanufacturing a first piston body c916. The first piston body c916 maydefine at least a portion of the first monolithic body c908 or at leasta portion of the first monolithic body-segment c912. Additionally, or inthe alternative, the first piston body c916 may define at least aportion of the second monolithic body c936 or at least a portion of thesecond monolithic body-segment c914. The exemplary method c4000 mayadditionally or alternatively include installing the first pistonassembly c090 in the first piston body c916.

The exemplary method 1000 may additionally or alternatively include, atblock c4014, additively manufacturing a first machine body c922. Thefirst machine body c922 may define at least a portion of the firstmonolithic body c908 or at least a portion of the first monolithicbody-segment c912. Additionally, or in the alternative, the firstmachine body c922 may define at least a portion of the second monolithicbody c936 or at least a portion of the second monolithic body-segmentc912. The exemplary method c4000 may additionally or alternativelyinclude installing the first load device c092 in the first machine bodyc922.

The exemplary method 1000 may additionally or alternatively include, atblock c4016, additively manufacturing a first regenerator body c926. Thefirst regenerator body c926 may define at least a portion of the firstmonolithic body c908 or at least a portion of the first monolithicbody-segment c912. Additionally, or in the alternative, the firstregenerator body c926 may define at least a portion of the secondmonolithic body c936 or at least a portion of the second monolithicbody-segment c912. The exemplary method c4000 may additionally oralternatively include installing the first regenerator body c926 in thefirst monolithic body c908 or at least a portion of the first monolithicbody-segment c912.

The exemplary method 1000 may additionally or alternatively include, atblock c4018, additively manufacturing a first chiller body c928. Thefirst chiller body c928 may define at least a portion of the firstmonolithic body c908 or at least a portion of the first monolithicbody-segment c912. Additionally, or in the alternative, the firstchiller body c928 may define at least a portion of the second monolithicbody c936 or at least a portion of the second monolithic body-segmentc912. The exemplary method c4000 may additionally or alternativelyinclude installing the first chiller body c928 in the first monolithicbody c908 or at least a portion of the first monolithic body-segmentc912.

As used herein, the terms “additively manufactured” or “additivemanufacturing techniques or processes” refer generally to manufacturingprocesses wherein successive layers of material(s) are provided on eachother to “build-up,” layer-by-layer, a three-dimensional component. Thesuccessive layers generally fuse together to form a monolithic componentwhich may have a variety of integral sub-components.

Although additive manufacturing technology is described herein asproviding fabrication of complex objects by building objectspoint-by-point, layer-by-layer, typically in a vertical direction, othermethods of fabrication are possible and are within the scope of thepresent subject matter. For example, although the discussion hereinrefers to the addition of material to form successive layers, oneskilled in the art will appreciate that the methods and structuresdisclosed herein may be practiced with any additive manufacturingtechnique or manufacturing technology. For example, embodiments of thepresent disclosure may use layer-additive processes, layer-subtractiveprocesses, or hybrid processes. As another example, embodiments of thepresent disclosure may include selectively depositing a binder materialto chemically bind portions of the layers of powder together to form agreen body article. After curing, the green body article may bepre-sintered to form a brown body article having substantially all ofthe binder removed, and fully sintered to form a consolidated article.

Suitable additive manufacturing techniques in accordance with thepresent disclosure include, for example, Fused Deposition Modeling(FDM), Selective Laser Sintering (SLS), 3D printing such as by inkjetsand laserjets, Sterolithography (SLA), Direct Laser Sintering (DLS),Direct Selective Laser Sintering (DSLS), Electron Beam Sintering (EBS),Electron Beam Melting (EBM), Laser Engineered Net Shaping (LENS), LaserNet Shape Manufacturing (LNSM), Direct Metal Deposition (DMD), DigitalLight Processing (DLP), Direct Laser Melting (DLM), Direct SelectiveLaser Melting (DSLM), Selective Laser Melting (SLM), Direct Metal LaserMelting (DMLM), Binder Jetting (BJ), and other known processes.

The additive manufacturing processes described herein may be used forforming components using any suitable material. For example, thematerial may be plastic, metal, concrete, ceramic, polymer, epoxy,photopolymer resin, or any other suitable material that may be in solid,liquid, powder, sheet material, wire, or any other suitable form orcombinations thereof. More specifically, according to exemplaryembodiments of the present subject matter, the additively manufacturedcomponents described herein may be formed in part, in whole, or in somecombination of materials including but not limited to pure metals,nickel alloys, chrome alloys, titanium, titanium alloys, magnesium,magnesium alloys, aluminum, aluminum alloys, and nickel or cobalt basedsuperalloys (e.g., those available under the name Inconel® availablefrom Special Metals Corporation). These materials are examples ofmaterials suitable for use in the additive manufacturing processesdescribed herein, and may be generally referred to as “additivematerials.”

In addition, one skilled in the art will appreciate that a variety ofmaterials and methods for bonding those materials may be used and arecontemplated as within the scope of the present disclosure. As usedherein, references to “fusing” or “binding” may refer to any suitableprocess for creating a bonded layer of any of the above materials. Forexample, if an object is made from polymer, fusing may refer to creatinga thermoset bond between polymer materials. If the object is epoxy, thebond may be formed by a crosslinking process. If the material isceramic, the bond may be formed by a sintering process. If the materialis powdered metal, the bond may be formed by a melting or sinteringprocess, or additionally with a binder process. One skilled in the artwill appreciate that other methods of fusing materials to make acomponent by additive manufacturing are possible, and the presentlydisclosed subject matter may be practiced with those methods.

In addition, the additive manufacturing process disclosed herein allowsa single component to be formed from multiple materials. Thus, thecomponents described herein may be formed from any suitable mixtures ofthe above materials. For example, a component may include multiplelayers, segments, or parts that are formed using different materials,processes, and/or on different additive manufacturing machines. In thismanner, components may be constructed which have different materials andmaterial properties for meeting the demands of any particularapplication. In addition, although the components described herein areconstructed entirely by additive manufacturing processes, it should beappreciated that in alternate embodiments, all or a portion of thesecomponents may be formed via casting, machining, and/or any othersuitable manufacturing process. Indeed, any suitable combination ofmaterials and manufacturing methods may be used to form thesecomponents.

An exemplary additive manufacturing process will now be described.Additive manufacturing processes fabricate components usingthree-dimensional (3D) information, for example a three-dimensionalcomputer model, of the component. Accordingly, a three-dimensionaldesign model of the component may be defined prior to manufacturing. Inthis regard, a model or prototype of the component may be scanned todetermine the three-dimensional information of the component. As anotherexample, a model of the component may be constructed using a suitablecomputer aided design (CAD) program to define the three-dimensionaldesign model of the component.

The design model may include 3D numeric coordinates of the entireconfiguration of the component including both external and internalsurfaces of the component. For example, the design model may define thebody, the surface, and/or internal passageways such as openings, supportstructures, etc. In one exemplary embodiment, the three-dimensionaldesign model is converted into a plurality of slices or segments, e.g.,along a central (e.g., vertical) axis of the component or any othersuitable axis. Each slice may define a thin cross section of thecomponent for a predetermined height of the slice. The plurality ofsuccessive cross-sectional slices together form the 3D component. Thecomponent is then “built-up” slice-by-slice, or layer-by-layer, untilfinished.

In this manner, the components described herein may be fabricated usingthe additive process, or more specifically each layer is successivelyformed, e.g., by fusing or polymerizing a plastic using laser energy orheat or by sintering or melting metal powder. For example, a particulartype of additive manufacturing process may use an energy beam, forexample, an electron beam or electromagnetic radiation such as a laserbeam, to sinter or melt a powder material. Any suitable laser and laserparameters may be used, including considerations with respect to power,laser beam spot size, and scanning velocity. The build material may beformed by any suitable powder or material selected for enhancedstrength, durability, and useful life, particularly at hightemperatures.

Each successive layer may be, for example, between about 10 μm and 200μm, although the thickness may be selected based on any number ofparameters and may be any suitable size according to alternativeembodiments. Therefore, utilizing the additive formation methodsdescribed above, the components described herein may have cross sectionsas thin as one thickness of an associated powder layer, e.g., 10 μm,utilized during the additive formation process.

In addition, utilizing an additive process, the surface finish andfeatures of the components may vary as need depending on theapplication. For example, the surface finish may be adjusted (e.g., madesmoother or rougher) by selecting appropriate laser scan parameters(e.g., laser power, scan speed, laser focal spot size, etc.) during theadditive process, especially in the periphery of a cross-sectional layerwhich corresponds to the part surface. For example, a rougher finish maybe achieved by increasing laser scan speed or decreasing the size of themelt pool formed, and a smoother finish may be achieved by decreasinglaser scan speed or increasing the size of the melt pool formed. Thescanning pattern and/or laser power can also be changed to change thesurface finish in a selected area.

After fabrication of the component is complete, various post-processingprocedures may be applied to the component. For example, post processingprocedures may include removal of excess powder by, for example, blowingor vacuuming. Other post processing procedures may include a stressrelief process. Additionally, thermal, mechanical, and/or chemical postprocessing procedures can be used to finish the part to achieve adesired strength, surface finish, a decreased porosity decreasing and/oran increased density (e.g., via hot isostatic pressing), and othercomponent properties or features.

It should be appreciated that one skilled in the art may add or modifyfeatures shown and described herein to facilitate manufacture of thesystem A10 provided herein without undue experimentation. For example,build features, such as trusses, grids, build surfaces, or othersupporting features, or material or fluid ingress or egress ports, maybe added or modified from the present geometries to facilitatemanufacture of embodiments of the system A10 based at least on a desiredmanufacturing process or a desired particular additive manufacturingprocess.

Notably, in exemplary embodiments, several features of the componentsdescribed herein were previously not possible due to manufacturingrestraints. However, the present inventors have advantageously utilizedcurrent advances in additive manufacturing techniques to developexemplary embodiments of such components generally in accordance withthe present disclosure. While certain embodiments of the presentdisclosure may not be limited to the use of additive manufacturing toform these components generally, additive manufacturing does provide avariety of manufacturing advantages, including ease of manufacturing,reduced cost, greater accuracy, etc.

In this regard, utilizing additive manufacturing methods, evenmulti-part components may be formed as a single piece of continuousmetal, and may thus include fewer sub-components and/or joints comparedto prior designs. The integral formation of these multi-part componentsthrough additive manufacturing may advantageously improve the overallassembly process, reduce potential leakage, reduce thermodynamic losses,improve thermal energy transfer, or provide higher power densities. Forexample, the integral formation reduces the number of separate partsthat must be assembled, thus reducing associated time, overall assemblycosts, reduces potential leakage pathways, or reduces potentialthermodynamic losses. Additionally, existing issues with, for example,leakage, may advantageously be reduced. Still further, joint qualitybetween separate parts may be addressed or obviated by the processesdescribed herein, such as to desirably reduce leakage, assembly, andimprove overall performance.

Also, the additive manufacturing methods described above provide muchmore complex and intricate shapes and contours of the componentsdescribed herein to be formed with a very high level of precision. Forexample, such components may include thin additively manufacturedlayers, cross sectional features, and component contours. As anotherexample, additive manufacturing may provide heat exchanger surfaceareas, volumes, passages, conduits, or other features that may desirablyimprove heat exchanger efficiency or performance, or overall engine orsystem performance. In addition, the additive manufacturing processprovides the manufacture of a single component having differentmaterials such that different portions of the component may exhibitdifferent performance characteristics. The successive, additive steps ofthe manufacturing process provide the construction of these novelfeatures. As a result, the components described herein may exhibitimproved functionality and reliability.

An exemplary engine c002 is shown in FIG. 14. The engine c002 may be aclosed cycle engine, such as a regenerative heat engine and/or aStirling engine; however other engines including other closed-cycleengines and/or regenerative heat engines are also contemplated and thescope of the present disclosure embraces any engine. A closed-cycleengine c002 may include a heater body c100 and an engine body c050. Inthe embodiment shown, a closed-cycle engine c002 may include an enginebody c050 and a heater body c100 disposed on opposite sides of theengine body c050. For example, a first heater body c100 may be disposedat a first side of an engine body c050 and a second heater body c100 maybe disposed at a second side of an engine body c050. In still otherembodiments, a plurality of engine bodies c050 may be provided and/or asingle heater body c100 or a multitude of heater bodies c100 may beprovided. The closed-cycle engine c002 may include a piston assemblyc090 and a load device c092 operably inserted within an engine body c050and/or a heater body c100.

The closed-cycle engine c002 may be provided in the form of an engineassembly that includes one or more monolithic bodies or monolithicbody-segments as described herein. A monolithic body and/or a monolithicbody-segment may be fabricated using an additive manufacturingtechnology and may be void of any seams, joints, or the likecharacteristic of separately fabricated components. By way of example,an exemplary closed-cycle engine c002 may be assembled from an engineassembly that includes a first heater body c100 and a first engine bodyc050. The first heater body may define a first portion of a firstmonolithic body or a first monolithic body-segment, and the first enginebody may define a second portion of the first monolithic body or asecond monolithic body-segment operably coupled or operably couplable tothe first heater body.

Now turning to FIGS. 15, 16, and 17 exemplary heater bodies c100 will bedescribed. The presently disclosed heater bodies c100 may be used tosupply heat to a closed-cycle engine c002 such as a regenerative heatengine and/or a Stirling engine. However, it will be appreciated thatthe presently disclosed heater bodies c100 may be used as a heatingsource in a number of other settings, all of which are within the scopeof the present disclosure. In some embodiments, at least a portion ofthe heater body c100 may define at least a portion of a closed-cycleengine c002, such as a monolithic body or a monolithic body-segment ofsuch a closed-cycle engine c002. For example, the monolithic body may bean additively manufactured monolithic body, or the monolithicbody-segment may be an additively manufactured monolithic body-segment.However, in addition or as an alternative to additive manufacturingtechnology, it will be appreciated that the monolithic body or variousmonolithic body-segments of a closed-cycle engine c002 may be formedusing any desired technology, all of which are within the scope of thepresent disclosure.

As shown, an exemplary heater body c100 may include a combustion chamberc102 and a recirculation pathway c104 configured to recirculatecombustion gas through the combustion chamber c102. The recirculationpathway c104 may include a hot-side heat exchanger c106 configured totransfer heat from circulating combustion gas to a heat input source,such as a working-fluid body c108 defining a heat transfer region havinga thermally conductive relationship with at least a portion of thehot-side heat exchanger c106. For example, heat from the combustion gasmay be transferred to the heat transfer region via an engine-workingfluid disposed within a working-fluid pathway c110. The working-fluidpathway c110 may be defined at least in part by the hot-side heatexchanger c106 and/or at least in part by the working-fluid body c108.The hot-side heat exchanger c106 may define a portion of therecirculation pathway c104. The heat transfer region may define a regionhaving a have a thermally conductive relationship with the heating fluidpathway.

The heat transfer region defined by the working-fluid body c108 mayinclude a solid body and/or a fluid pathway defined at least in part bythe solid body. In an exemplary embodiment, the hot-side heat exchangerc106 may include a plurality of heating fluid pathways that have a heattransfer relationship with a plurality of heat transfer regions. Forexample, the plurality of heat transfer regions have a thermallyconductive relationship with a corresponding portion of the plurality ofheating fluid pathways. Additionally, or in the alternative, the heattransfer regions may have a thermally convective relationship with aheating fluid flowing through the heating fluid pathways. The heattransfer regions may be circumferentially spaced about the longitudinalaxis of the heater body c100. Respective ones of the plurality of heattransfer regions may include a solid body and/or a fluid pathway definedat least in part by the solid body.

The working-fluid body c108 may include one or more portions of aclosed-cycle engine c002, such as a piston chamber c112 (e.g., a hotpiston chamber) and/or a regenerator body c114. A fluid pathway definedthe working-fluid body c108 may fluidly communicate with the pistonchamber and the regenerator body c114. The engine-working fluid disposedwithin the working-fluid pathway c110 may be an engine-working fluid,such as an inert gas, which may flow in an alternating fashion betweenthe piston chamber c112 and the regenerator body c114. The hot-side heatexchanger c106 may be provided in the form of a heat exchanger body. Theheat exchanger body may define a monolithic body portion of the heaterbody c100 or a monolithic body-segment operably coupled or operablycouplable to a monolithic heater body c100 or to one or more othermonolithic body-segments that make up the heater body c100.

In an exemplary embodiment, transferring heat from the combustion gas inthe hot-side heat exchanger c106 at block c154 may include transferringheat to a working-fluid body c108. The working-fluid body c108 mayinclude a solid body and/or fluid in a fluid pathway defined at least inpart by the solid body. The heat transferring to the working-fluid bodyc108 may come from combustion gas flowing through a plurality of heatingfluid pathways defined at least in part by the hot-side heat exchangerc106. The heat may be transferred to respective ones of a plurality ofheat transfer regions that have a thermally conductive relationship witha corresponding portion of the plurality of heating fluid pathways. Theworking-fluid body c108 may include a plurality of working-fluidpathways, and the exemplary method c150 may include flowing fluidthrough the working-fluid pathways as heat transfers thereto from thehot-side heat exchanger c106. In some embodiments, the working-fluidpathways may fluidly communicate with a piston chamber and a regeneratorof a closed-cycle engine c002, and the exemplary method may includeflowing fluid through the working-fluid pathways alternatingly betweenthe regenerator and the piston chamber.

An exemplary heater body c100 may additionally or alternatively includea working-fluid body c108. A working-fluid body c108 may include any oneor more bodies that receive a heat input from the hot-side heatexchanger body c600. An exemplary working-fluid body c108 may includeone or more piston bodies c700 and/or one or more regenerator bodiesc800. An exemplary working-fluid body c108 may additionally oralternatively include one or more working-fluid pathways c110, such asone or more working-fluid pathways c110 fluidly communicating with atleast one piston body c700 and/or at least one regenerator body c800. Aworking-fluid body c108 may be monolithically integrated with thehot-side heat exchanger body c600. In some embodiments, theworking-fluid body c108 may define at least a portion of a plurality ofworking-fluid pathways. Additionally, or in the alternative, in someembodiments the hot-side heat exchanger body c600 may define at least aportion of the plurality of working-fluid pathways.

Now referring to FIG. 17 exemplary monolithic bodies defining at least aportion of a heater body c100 will be described. Exemplary monolithicbodies may be formed as one single monolithic body. Various portions ofa monolithic body are sometimes referred to as monolithic body portions.Additionally, or in the alternative, exemplary monolithic bodies mayinclude a plurality of segments combinable to form a monolithic body.Such segments are sometimes referred to herein as monolithicbody-segments. As shown in FIG. 17, an exemplary heater body c100 mayinclude a combustor body c400, a fuel injector body c401, a hot-sideheat exchanger body c600, an eductor body c300, a heat recuperator bodyc500, and/or a working-fluid body c108. The combustor body c400, thefuel injector body c401, the hot-side heat exchanger body c600, theeductor body c300, the heat recuperator body c500, and/or theworking-fluid body c108 may respectively define monolithic body portionsof the heater body c100 and/or monolithic body-segments of the heaterbody c100.

An exemplary heater body c100 may include a combustor body c400. Thecombustor body c400 may include a combustion chamber body c402 definingat least a portion of a combustion chamber c102. The combustion chamberbody c402 and/or the combustion chamber c102 may be disposed annularlyabout an axis c204. The combustor body c400 may additionally include aconditioning conduit body c404 defining at least a portion of aconditioning conduit c122 circumferentially surrounding the combustionchamber c102. The combustion chamber body c402 and the conditioningconduit body c404 may be monolithically integrated with the heater bodyc100 at a distal portion of the heater body c100 such that theconditioning conduit may fluidly communicate with the combustion chamberc102 at a distal portion of the combustion chamber c102. For example,the conditioning conduit body c404 may be monolithically integrated withthe combustion chamber body c402. Alternatively, the combustion chamberbody c402 and the conditioning conduit body c404 may define monolithicbody-segments operably couplable to one another and/or to the heaterbody c100 or another monolithic body-segment thereof so as to provide anintegrally formed combustor body c400.

An exemplary heater body c100 may additionally or alternatively includea fuel injector body c401. The fuel injector body c401 may bemonolithically integrated with the heater body c100 at a distal portionc202 of the heater body c100, such as at a distal portion c202 of thecombustion chamber c102. For example, the fuel injector body c401 may bemonolithically integrated with the combustor body c400 (e.g., with thecombustion chamber body c402 and/or the conditioning conduit body c404).Alternatively, the fuel injector body c401 and the combustor body c400(e.g., the combustion chamber body c402 and/or the conditioning conduitbody c404) may define monolithic body-segments operably couplable to oneanother and/or to the heater body c100 or another monolithicbody-segment thereof.

An exemplary heater body c100 may additionally or alternatively includea hot-side heat exchanger body c600. The hot-side heat exchanger bodyc600 may include a plurality of heating fluid pathways and a pluralityof heat transfer regions. The plurality of heating fluid pathways may becircumferentially spaced about an inlet plenum fluidly communicatingwith the plurality of heating fluid pathways. In some embodiments,respective ones of the plurality of heating fluid pathways may define aspiral pathway. Respective ones of the plurality of heat transferregions may have a heat transfer relationship with a correspondingsemiannular portion of the plurality of heating fluid pathways.

The hot-side heat exchanger body c600 may be monolithically integratedwith the heater body c100 at a proximal portion c200 of the heater bodyc100 such that the combustion chamber c102 may fluidly communicate withthe plurality of heating fluid pathways at a proximal portion c200 ofthe combustion chamber c102. For example, the hot-side heat exchangerbody c600 may be monolithically integrated with the combustor body c400(e.g., with the combustion chamber body c402 and/or the conditioningconduit body c404). Alternatively, the hot-side heat exchanger body c600and the combustor body c400 (e.g., the combustion chamber body c402and/or the conditioning conduit body c404) may define monolithicbody-segments operably couplable to one another and/or to the heaterbody c100 or another monolithic body-segment thereof.

An exemplary heater body c100 may additionally or alternatively includean eductor body c300. The eductor body c300 may be monolithicallyintegrated with the hot-side heat exchanger body c600 and/or thecombustor body c400 (e.g., the conditioning conduit body c404) such thatthe plurality of heating fluid pathways may fluidly communicate with aradially or concentrically outward portion of the an education pathwaydefined by the eductor body c300. In some embodiments, the exemplaryheater body c100 may include a recirculation annulus body c302configured to provide fluid communication between the plurality ofheating fluid pathways of the hot-side heat exchanger body c600 and thecombustor body c400 (e.g., the conditioning conduit body c404).

An exemplary heater body c100 may additionally or alternatively includea heat recuperator body c500. The heat recuperator body c500 may bemonolithically integrated with the eductor body c300. In someembodiments, the exemplary heater body c100 may include an intakeannulus body c502, an exhaust annulus body c504, and/or a motive annulusbody c506. The intake annulus body c502 may be monolithically integratedwith the heat recuperator body c500 such that the intake annulus bodyc502 and the heat recuperator body c500 define at least a portion of anintake air pathway c118. The exhaust annulus body c504 may bemonolithically integrated the heat recuperator body c500 such that theexhaust annulus body c504 and the heat recuperator body c500 define atleast a portion of the exhaust pathway c120. The motive annulus bodyc502 may be monolithically integrated with the heat recuperator bodyc500 and the eductor body c300 such that the motive annulus body definesat least a portion of the intake air pathway c118 between the heatrecuperator body c500 and the eductor body c300.

An exemplary heater body c100 may additionally or alternatively includea working-fluid body c108. A working-fluid body c108 may include any oneor more bodies that receive a heat input from the hot-side heatexchanger body c600. An exemplary working-fluid body c108 may includeone or more piston bodies c700 and/or one or more regenerator bodiesc800. An exemplary working-fluid body c108 may additionally oralternatively include one or more working-fluid pathways c110, such asone or more working-fluid pathways c110 fluidly communicating with atleast one piston body c700 and/or at least one regenerator body c800. Aworking-fluid body c108 may be monolithically integrated with thehot-side heat exchanger body c600. In some embodiments, theworking-fluid body c108 may define at least a portion of a plurality ofworking-fluid pathways. Additionally, or in the alternative, in someembodiments the hot-side heat exchanger body c600 may define at least aportion of the plurality of working-fluid pathways.

Now referring to FIG. 18 exemplary hot-side heat exchanger bodies c600will be described. The presently disclosed hot-side heat exchangerbodies c600 may define part of a heater body c100 and/or a closed-cycleengine c002. For example, a hot-side heat exchanger body c600 may defineat least a portion of a monolithic body or a monolithic body-segment.Such monolithic body or monolithic body-segment may define at least aportion of the heater body c100 and/or the closed-cycle engine c002.Additionally, or in the alternative, the presently disclosed hot-sideheat exchanger bodies c600 may be provided as a separate component,whether for use in connection with a heater body c100, a closed-cycleengine c002, or any other setting whether related or unrelated to aheater body c100 or a closed-cycle engine c002. At least a portion ofthe hot-side heat exchanger body c600 may define a hot-side heatexchanger c106. While the heater bodies c100 depicted in the figures mayshow one hot-side heat exchanger body c600 and/or one hot-side heatexchanger c106, it will be appreciated that a heater body c100 mayinclude a plurality of hot-side heat exchanger bodies c600 and/or aplurality of hot-side heat exchangers c106. For example, a heater bodyc100 may include one or more hot-side heat exchanger bodies c600, and/ora hot-side heat exchanger body c600 may include one or more hot-sideheat exchangers c106.

As shown, for example, in FIG. 18, the hot-side heat exchanger body c600and/or a working-fluid body c108 may define a plurality of heat transferregions c612. The plurality of heat transfer regions c612 may correspondto respective portions of a working-fluid body c108. A respective heattransfer region c612 may encompass a portion of the hot-side heatexchanger body c600 and/or a portion of the working-fluid body c108.Respective ones of the plurality of heat transfer regions c612 have athermally conductive relationship with a corresponding portion c614 ofthe plurality of heating fluid pathways c602, such as a semiannularportion c614 of the plurality of heating fluid pathways c602.

Respective ones of the plurality of heat transfer regions c612 mayinclude a heat input region, at least one heat extraction region, and aplurality of working-fluid pathways c110. The heat input region mayinclude a piston body c700 and the heat extraction region may include aregenerator body c800.

In some embodiments, a heat transfer region c612 may include at last aportion of a working-fluid body c108. For example, a heat transferregion c612 may include at least a portion of a piston body c700 and/orat least a portion of a regenerator body c800. Additionally, or in thealternative, a heat transfer region c612 include one or moreworking-fluid pathways c110 that have a thermally conductiverelationship with a corresponding portion c614 (e.g., a semiannularportion) of at least some of the plurality of heating fluid pathwaysc602. For example, the heat transfer region c612 may include one or moreworking-fluid pathways c110 defined at least in part within acorresponding one or more heating wall c616 of a hot-side heat exchangerc106. Such working-fluid pathways c110 may define a pathway for anengine-working fluid to flow through the hot-side heat exchanger c106,such as through the one or more heating walls c616 thereof. Where aworking-fluid pathway c110 flows through a hot-side heat exchanger c106,the heat transfer region c612 may include a portion of the working-fluidpathway within or defined by the hot-side heat exchanger c106, such aswithin a region of one or more heating wall c616 of the hot-side heatexchanger c106 corresponding to the heat transfer region c612.

As shown, for example, in FIG. 18, at least some of the working-fluidpathways c110 may be radially or concentrically adjacent to one another.Additionally, or in the alternative, as also shown, at least some of theworking-fluid pathways c110 may be semiannular to one another. Theworking-fluid pathways c110 may fluidly communicate between the heatinput region and the at least one heat extraction region. The pluralityof heating fluid pathways c602 may be disposed radially orconcentrically adjacent to corresponding respective ones of theplurality of working-fluid pathways c110, such as radially orconcentrically adjacent to respective ones of a plurality of semiannularworking-fluid pathways c110. Respective ones of the plurality of heatingfluid pathways c602 may have a thermally conductive relationship withcorresponding respective ones of the plurality of working-fluid pathwaysc110.

In some embodiments, a heat transfer region c622 may include a pistonbody c700 and/or a regenerator body c800, and/or a plurality ofworking-fluid pathways c110 fluidly communicating between the pistonbody c700 and/or the regenerator body c800. When a closed-cycle enginec002 includes a plurality of piston bodies, the piston assemblies mayhave a staggered or offset stroke cycle, such that a first piston and asecond piston may be located at different points in respective strokecycles upon least one point of the stroke cycle. For example, the firstpiston may be at a top point of the stroke cycle and the second pistonmay be at a bottom point of the stroke cycle. As another example, thefirst piston may be at a midpoint of the stroke cycle and the secondpiston may be at the top point or the bottom point of the stroke cycle.In some embodiments, engine-working fluid flowing from a piston bodyc700 (e.g., from a piston chamber c112) to a regenerator body c800 mayexhibit a temperature that differs from engine-working fluid flowing inthe opposite direction, from the regenerator body c800 to the pistonbody c700 (e.g., to the piston chamber c112).

The engine-working fluid flowing through the working-fluid pathways c110may exhibit a temperature that depends at least in part on whether theengine-working fluid is flowing towards the regenerator body c800 (e.g.,from the piston body c700) or towards the piston body c700 (e.g., fromthe regenerator body c800). For example, the temperature of theengine-working fluid may exhibit a first temperature when flowingtowards the regenerator body c800 (e.g., from the piston body c700) anda second temperature when flowing towards the piston body c700 (e.g.,from the regenerator body c800). In some embodiments the firsttemperature may be greater than the second temperature.

In some embodiments, the heating fluid such as combustion gas and theengine-working fluid may exhibit a temperature gradient that depends atleast in part on whether the engine-working fluid is flowing towards theregenerator body c800 (e.g., from the piston body c700) or towards thepiston body c700 (e.g., from the regenerator body c800). For example, afirst temperature gradient may correspond to engine-working fluidflowing towards the regenerator body c800 (e.g., from the piston bodyc700) and a second temperature gradient may correspond to engine-workingfluid flowing towards the piston body c700 (e.g., from the regeneratorbody c800). In some embodiments the first temperature gradient may besmaller than the second temperature gradient. In some embodiments thesecond temperature gradient may be greater than the first temperaturegradient. For example, the first temperature gradient may be smallerthan the second temperature gradient at least in part because of thetemperature of the engine-working fluid flowing towards the regeneratorbody c800 (e.g., from the piston body c700) being greater than thetemperature of engine-working fluid flowing towards the piston body c700(e.g., from the regenerator body c800).

In some embodiments, the rate and/or quantity of heat transfer from theheating fluid to the engine-working fluid may depend on whether theengine-working fluid is flowing towards the regenerator body c800 (e.g.,from the piston body c700) or towards the piston body c700 (e.g., fromthe regenerator body c800). For example, a first rate and/or quantity ofheat transfer from the heating fluid to the engine-working fluid maycorrespond to engine-working fluid flowing towards the regenerator bodyc800 (e.g., from the piston body c700) and a second rate and/or quantityof heat transfer from the heating fluid to the engine-working fluid maycorrespond to engine-working fluid flowing towards the piston body c700(e.g., from the regenerator body c800). In some embodiments the firstrate and/or quantity of heat transfer may be smaller than the secondrate and/or quantity of heat transfer. In other words, the second rateand/or quantity of heat transfer may be greater than the first rateand/or quantity of heat transfer. For example, the first rate and/orquantity of heat transfer may be smaller than the second rate and/orquantity of heat transfer at least in part because of the firsttemperature gradient corresponding to engine-working fluid flowingtowards the regenerator body c800 (e.g., from the piston body c700)being smaller than the second temperature gradient corresponding toengine-working fluid flowing towards the piston body c700 (e.g., fromthe regenerator body c800).

In some embodiments, the heating efficiency of the heater body c100 maybe enhanced at least in part by the second rate and/or quantity of heattransfer corresponding to engine-working fluid flowing towards thepiston body c700 (e.g., from the regenerator body c800) being greaterthan the first rate and/or quantity of heat transfer corresponding toengine-working fluid flowing towards the regenerator body c800 (e.g.,from the piston body c700). For example, in this way, a relativelylarger proportion of the heat input by the heater body c100 may beapplied to the engine-working fluid as the engine-working fluid flowstowards the piston body c700 and thereby drives the piston downward,performing the downstroke portion of a stroke cycle. The heat input tothe engine-working fluid during the downstroke may contribute to thedownstroke (e.g., directly) by further heating and thereby furtherexpanding the engine-working fluid. During the upstroke portion of thestroke cycle, a relatively smaller proportion of the heat input by theheater body c100 may be applied to the engine-working fluid, which mayreduce or mitigate a potential for heat input to the engine-workingfluid to counteract the upstroke by further heating and therebyexpanding the engine-working fluid, providing an additional oralternative efficiency enhancement. With a relatively smaller proportionof the heat input by the heater body c100 applied to the engine-workingfluid during the upstroke, a smaller portion of the heat input may betransferred to the regenerator body c800. While the regenerator bodyc800 may be configured to retain heat, at least some heat transferringto the regenerator body c800 may be lost. By transferring a largerproportion of the heat input of the heater body c100 to theengine-working fluid when flowing towards the piston body c700 (e.g.,from the regenerator body c800), less heat energy may be lost to theregenerator body c800, thereby providing yet another additional oralternative efficiency enhancement.

In some embodiments, at least a portion of the heater body c100 (e.g.,the hot-side heat exchanger body c600 and/or the working-fluid bodyc108) may be configured such that the temperature gradient between thetemperature gradient between the heating fluid and the engine-workingfluid is relatively small when the engine-working fluid is flowingtowards the regenerator body c800. For example, the temperature gradientbetween the heating fluid and the engine-working fluid may be minimalwhen the engine-working fluid is flowing towards the regenerator bodyc800. With a relatively small and/or minimal temperature gradient, therate and/or quantity of heat transfer to the engine-working fluid whenflowing towards the regenerator body c800 may be minimal or nominal.Additionally, or in the alternative, at least a portion of the heaterbody c100 (e.g., the hot-side heat exchanger body c600 and/or theworking-fluid body c108) may be configured such that the temperaturegradient between the temperature gradient between the heating fluid andthe engine-working fluid is relatively large when the engine-workingfluid is flowing towards the piston body c700. For example, thetemperature gradient between the heating fluid and the engine-workingfluid may be maximal when the engine-working fluid is flowing towardsthe piston body c700. With a relatively large and/or maximal temperaturegradient, the rate and/or quantity of heat transfer to theengine-working fluid when flowing towards the regenerator body c800 maybe maximized.

In some embodiments, the rate and/or quantity of heat transferred fromthe heating fluid to the engine-working fluid may exhibit a ratio ofheat transfer when flowing towards the piston body c700 to heat transferwhen flowing towards the regenerator body c800 of from about 1:1 toabout 100:1, such as from about 2:1 to about 100:1, such as from about2:1 to about 10:1, such as from about 10:1 to about 20:1, such as fromabout 20:1 to about 50:1, or such as from about 50:1 to about 100:1. Theratio may be at least 1:1, such as at least 2:1, such as at least 10:1,such as at least 20:1, such as at least 50:1, or such as at least 90:1.The ratio may be less than 100:1, such as less than 90:1, such as lessthan 50:1, such as less than 20:1, such as less than 10:1, or such asless than 2:1.

Now referring to FIGS. 19 and 20, exemplary working-fluid bodies c108will be described. The presently disclosed working-fluid bodies c108 maydefine part of a heater body c100 and/or a closed-cycle engine c002. Forexample, a working-fluid body c108 may define at least a portion of amonolithic body or a monolithic body-segment. Such monolithic body ormonolithic body-segment may define at least a portion of the heater bodyc100 and/or the closed-cycle engine c002. Additionally, or in thealternative, the presently disclosed working-fluid bodies c108 may beprovided as a separate component, whether for use in connection with aheater body c100, a closed-cycle engine c002, or any other settingwhether related or unrelated to a heater body c100 or a closed-cycleengine c002. At least a portion of the working-fluid bodies c108 maydefine a one or more piston bodies c700, one or more regenerator bodiesc800, and/or one or more working-fluid pathway c110. It will beappreciated that a heater body c100 may include any desired number ofworking-fluid bodies c108, including any desired number of piston bodiesc700, regenerator bodies c800, and/or working-fluid pathways c110. Forexample, a heater body c100 may include one or more working-fluid bodiesc108, and/or a working-fluid body c108 may include one or more pistonbodies c700, regenerator bodies c800, and/or working-fluid pathwaysc110.

A working-fluid body c108 may define a first portion of a monolithicbody and the piston body c700 may defines a second portion of themonolithic body. Alternatively, the piston body c700 may define amonolithic body-segment operably coupled or operably couplable to theworking-fluid body c108. Additionally, or in the alternative, aregenerator body c800 may a second portion of the monolithic body, orthe regenerator body c800 may define a second monolithic body-segmentoperably coupled or operably couplable to the piston body 700 and/or theworking-fluid body c108.

An exemplary working-fluid body c108 may include a plurality of heattransfer regions c612. Respective ones of the plurality of heat transferregions may include a plurality of working-fluid pathways c110 fluidlycommunicating between a heat input region and a heat extraction region.The heat input region may include a piston body c700 and the heatextraction region may include a regenerator body c800.

Now referring to FIG. 19, another exemplary cross-sectional view of aworking-fluid body c108 will be described. As shown in FIG. 19, aplurality of piston bodies c700 and a plurality of regenerator bodiesc800 may be circumferentially spaced about a longitudinal axis c204 ofthe working-fluid body c108. The plurality of piston bodies c700 andregenerator bodies c800 may be paired with one another, for example,with a plurality of working-fluid pathways c110 fluidly communicationbetween respective piston body c700 and regenerator body c800 pairs. Forexample, a first plurality of working-fluid pathways c701 may fluidlycommunicate between a first piston chamber c112 defined by a firstpiston body c700 and a first regenerator chamber c802 defined by a firstregenerator body c800. A second plurality of working-fluid pathways c702may fluidly communicate between a second piston chamber c112 defined bya second piston body c700 and a second regenerator chamber c802 definedby a second regenerator body c800. A third plurality of working-fluidpathways c703 may fluidly communicate between a third piston chamberc112 defined by a third piston body c700 and a third regenerator chamberc802 defined by a third regenerator body c800. A fourth plurality ofworking-fluid pathways c704 may fluidly communicate between a fourthpiston chamber c112 defined by a fourth piston body c700 and a fourthregenerator chamber c802 defined by a fourth regenerator body c800.

A flow direction of engine-working fluid flowing through a plurality ofworking-fluid pathways c110 may be counter-current or co-currentrelative to a flow direction c732 of heating fluid flowing through theheating fluid pathways c602 adjacent to such working-fluid pathwaysc110. For example, as shown, engine-working fluid flowing from a pistonchamber c112 towards a regenerator chamber c802 may be counter-currentto the flow direction c732 of the heating fluid flowing through adjacentheating fluid pathways c602. Engine-working fluid flowing from aregenerator chamber c802 towards a piston chamber c112 may be co-currentto the flow direction c732 of the heating fluid flowing through adjacentheating fluid pathways c602. Alternatively, in other embodiments,engine-working fluid may be counter-current to the flow direction c732of the heating fluid when flowing from a piston chamber c112 towards aregenerator chamber c802 and co-current when flowing from a regeneratorchamber c802 towards a piston chamber c112.

In a general sense, heat transfer from a hot fluid to a cold fluid maybe greater during counter-current flow relative to co-current flow. Forexample, with co-current flow, the temperature of the cold fluid may bealways less than the temperature of the hot fluid, and as such, heattransfer may be restricted by the discharge temperature of the coldfluid. Conversely, with counter-currently flow, heat transfer is notrestricted by the discharge temperature of the cold fluid, which mayallow for a greater quantity of heat transfer. On the other hand, withco-current flow, the temperature gradient between a hot fluid and a coldfluid may be greater at an initial zone of heat transfer prior toachieving thermal equilibrium, relative to the temperature gradient atan initial zone of heat transfer with counter-current flow. As such,faster heat transfer may be achieved during non-equilibrium conditionsduring co-current flow.

In some embodiments, it may be advantageous for heating fluid to flowco-currently relative to engine-working fluid when the engine-workingfluid flows from the regenerator body c800 to the piston body c700. Forexample, the temperature gradient between the engine-working fluid andthe heating fluid may be greater when the engine-working fluid flowsfrom the regenerator body c800 towards the piston body c700 relative toengine-working fluid flowing in the opposite direction. Such temperaturegradient may be greater, for example, because of heat losses as heattransfers from the engine-working fluid to the regenerator body c800 andback to the engine-working fluid. With a greater temperature gradientexisting when engine-working fluid flows from the regenerator body c800towards the piston body c700, such temperature gradient may facilitate amore rapid heat transfer from the heating fluid to the engine-workingfluid. In particular, such temperature gradient may facilitate a morerapid heat transfer to the engine-working fluid as the engine-workingfluid flows into the piston body c800, thereby further expanding theengine-working fluid and contributing to the downstroke (e.g., directly)of the piston within the piston chamber. Additionally, or in thealternative, with heating fluid flowing counter-current relative toengine-working fluid flowing from the piston body c700 to theregenerator body c800, the rate of heat transfer from the heating fluidto the engine-working fluid may be less than when the engine-workingfluid flows in the opposite direction. As such, relatively less heattransfer may be imparted to the engine-working fluid when flowing intothe regenerator body c800 the engine-working fluid flows from theregenerator body c800, further contributing to efficiency of the heaterbody c100, such as when inputting heat to the closed-cycle engine c002.

Control systems and methods of controlling various systems disclosedherein will now be provided. A control system generates control commandsthat are provided to one or more controllable devices of the system. Thecontrollable devices execute control actions in accordance with thecontrol commands. Accordingly, the desired output of the system can beachieved.

FIG. 21 provides an example computing system in accordance with anexample embodiment of the present disclosure. The one or morecontrollers, computing devices, or other control devices describedherein can include various components and perform various functions ofthe one or more computing devices of the computing system b2000described below.

As shown in FIG. 21, the computing system b2000 can include one or morecomputing device(s) b2002. The computing device(s) b2002 can include oneor more processor(s) b2004 and one or more memory device(s) b2006. Theone or more processor(s) b2004 can include any suitable processingdevice, such as a microprocessor, microcontroller, integrated circuit,logic device, and/or other suitable processing device. The one or morememory device(s) b2006 can include one or more computer-readable media,including, but not limited to, non-transitory computer-readable media,RAM, ROM, hard drives, flash drives, and/or other memory devices.

The one or more memory device(s) b2006 can store information accessibleby the one or more processor(s) b2004, including computer-readableinstructions b2008 that can be executed by the one or more processor(s)b2004. The instructions b2008 can be any set of instructions that whenexecuted by the one or more processor(s) b2004, cause the one or moreprocessor(s) b2004 to perform operations. In some embodiments, theinstructions b2008 can be executed by the one or more processor(s) b2004to cause the one or more processor(s) b2004 to perform operations, suchas any of the operations and functions for which the computing systemb2000 and/or the computing device(s) b2002 are configured, such as e.g.,operations for controlling certain aspects of power generation systemsand/or controlling one or more closed cycle engines as described herein.For instance, the methods described herein can be implemented in wholeor in part by the computing system b2000. Accordingly, the method can beat least partially a computer-implemented method such that at least someof the steps of the method are performed by one or more computingdevices, such as the exemplary computing device(s) b2002 of thecomputing system b2000. The instructions b2008 can be software writtenin any suitable programming language or can be implemented in hardware.Additionally, and/or alternatively, the instructions b2008 can beexecuted in logically and/or virtually separate threads on processor(s)b2004. The memory device(s) b2006 can further store data b2010 that canbe accessed by the processor(s) b2004. For example, the data b2010 caninclude models, databases, etc.

The computing device(s) b2002 can also include a network interface b2012used to communicate, for example, with the other components of system(e.g., via a network). The network interface b2012 can include anysuitable components for interfacing with one or more network(s),including for example, transmitters, receivers, ports, controllersb1510, antennas, and/or other suitable components. One or morecontrollable devices b1534 and other controllers b1510 can be configuredto receive one or more commands or data from the computing device(s)b2002 or provide one or more commands or data to the computing device(s)b2002.

The technology discussed herein makes reference to computer-basedsystems and actions taken by and information sent to and fromcomputer-based systems. One of ordinary skill in the art will recognizethat the inherent flexibility of computer-based systems allows for agreat variety of possible configurations, combinations, and divisions oftasks and functionality between and among components. For instance,processes discussed herein can be implemented using a single computingdevice or multiple computing devices working in combination. Databases,memory, instructions, and applications can be implemented on a singlesystem or distributed across multiple systems. Distributed componentscan operate sequentially or in parallel.

Although specific features of various embodiments may be shown in somedrawings and not in others, this is for convenience only. In accordancewith the principles of the present disclosure, any feature of a drawingmay be referenced and/or claimed in combination with any feature of anyother drawing.

This written description uses examples to describe the presentlydisclosed subject matter, including the best mode, and also to provideany person skilled in the art to practice the subject matter, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the presently disclosed subject matteris defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they include structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

1-20. (canceled)
 21. An engine body, comprising: a piston bodycomprising a piston chamber; a regenerator body comprising a regeneratorconduit; and a working-fluid heat exchanger body comprising a pluralityof working-fluid pathways fluidly communicating between the pistonchamber and the regenerator conduit; wherein the engine body comprises amonolithic body defined at least in part by the piston body, theregenerator body, and the working-fluid heat exchanger body.
 22. Theengine body of claim 21, comprising: a heater body comprising aplurality of heating fluid pathways having a heat transfer relationshipwith the plurality of working fluid pathways.
 23. The engine body ofclaim 22, wherein the heater body defines at least a portion of amonolithic body-segment coupled to the engine body.
 24. The engine bodyof claim 22, wherein the heater body defines a portion of the monolithicbody.
 25. The engine body of claim 21, comprising: a combustor bodydefining a combustion chamber.
 26. The engine body of claim 25, whereinthe combustor body defines at least a portion of a monolithicbody-segment coupled to the engine body.
 27. The engine body of claim26, comprising: a heater body comprising a plurality of heating fluidpathways having a heat transfer relationship with the plurality ofworking fluid pathways.
 28. The engine body of claim 27, wherein theplurality of heating fluid pathways fluidly communicate with thecombustion chamber.
 29. The engine body of claim 21, wherein theworking-fluid heat exchanger body comprises a plurality of heating fluidpathways having a heat transfer relationship with the plurality ofworking fluid pathways.
 30. The engine body of claim 21, wherein thepiston body comprises a plurality of piston chamber apertures fluidlycommunicating with the piston chamber, wherein the regenerator bodycomprises a plurality of regenerator apertures fluidly communicatingwith the regenerator conduit, and wherein the plurality of working-fluidpathways respectively fluidly communicate between respective ones of theplurality of piston chamber apertures and respective ones of theplurality of regenerator apertures.
 31. An engine body, comprising: apiston body comprising a piston chamber; a regenerator body comprising aregenerator conduit; and a heater body comprising a plurality of heatingfluid pathways and a plurality of working-fluid pathways, the pluralityof heating fluid pathways having a heat transfer relationship with theplurality of working fluid pathways, the plurality of working-fluidpathways fluidly communicating between the piston chamber and theregenerator conduit; wherein the engine body comprises a monolithic bodydefined at least in part by the piston body, the regenerator body, andthe heater body.
 32. The engine body of claim 21, comprising: acombustor body defining a combustion chamber.
 33. The engine body ofclaim 32, wherein the combustor body defines a monolithic body-segmentcoupled to the engine body.
 34. The engine body of claim 32, wherein thecombustor body defines a portion of the monolithic body.
 35. The enginebody of claim 32, wherein the plurality of heating fluid pathwaysfluidly communicate with the combustion chamber.
 36. The engine body ofclaim 32, wherein the piston body comprises a plurality of pistonchamber apertures fluidly communicating with the piston chamber, whereinthe regenerator body comprises a plurality of regenerator aperturesfluidly communicating with the regenerator conduit, and wherein theplurality of working-fluid pathways respectively fluidly communicatebetween respective ones of the plurality of piston chamber apertures andrespective ones of the plurality of regenerator apertures.
 37. An engineassembly, comprising: a plurality of engine bodies, wherein respectiveones of the plurality of engine bodies respectively define a firstmonolithic body, the first monolithic body comprising: a piston bodycomprising a piston chamber, a regenerator body comprising a regeneratorconduit, and a working-fluid heat exchanger body comprising a pluralityof working-fluid pathways fluidly communicating between the pistonchamber and the regenerator conduit; and a heater body defining a secondmonolithic body comprising a plurality of heating fluid pathways;wherein the plurality of engine bodies are coupled to the heater body,and wherein the plurality of heating fluid pathways have a heat transferrelationship with at least some of the plurality of working fluidpathways.
 38. The engine assembly of claim 37, comprising: a combustorbody defining a combustion chamber.
 39. The engine assembly of claim 38,wherein the combustor body defines at least a portion of the secondmonolithic body.
 40. The engine assembly of claim 38, wherein theplurality of heating fluid pathways fluidly communicate with thecombustion chamber.